八幡の藪知らず	1514
八幡の不知藪	0
八幡の薮知らず	82
八幡の薮不知	25

Good catch. I have proposed changing the order and hiding the marginal terms.
I have also proposed entries for 藪知らず and 八幡知らず (both in GG5).

@@ -6,3 +5,0 @@
-</k_ele>
-<k_ele>
-<keb>八幡の不知藪</keb>
@@ -17,0 +15,4 @@
+<k_ele>
+<keb>八幡の不知藪</keb>
+<ke_inf>&sK;</ke_inf>
+</k_ele>
@@ -20,0 +22,4 @@
+<sense>
+<pos>&n;</pos>
+<gloss>popular name for a bamboo grove in Chiba, famous for the legend that once you enter you can never leave</gloss>
+</sense>
@@ -34,4 +38,0 @@
-</sense>
-<sense>
-<pos>&n;</pos>
-<gloss>popular name for a bamboo grove in Chiba, famous for the legend that once you enter you can never leave (original meaning)</gloss>

I don't know where the form 八幡の不知藪 is *actually* used, but here the city of ichikawa acknowledges it
「八幡のやぶしらず（八幡の不知藪）」の項目があり、「八幡不知森（しらずのもり）
https://www.city.ichikawa.lg.jp/common/library/db/file/0000391087.pdf

For my sanity, here is a reference with pronunciation:
そのほか、伝説で知られる八幡の不知藪(やぶしらず)や、
https://kotobank.jp/word/市川(市)-1504691

According to wikipedia, in isolation the pronunciation may actually be different "しらずやぶ":
市川市が設けた解説板[要文献特定詳細情報]には、「不知八幡森（しらずやわたのもり）」と記されており、ほかに「不知森（しらずもり）」「不知藪（しらずやぶ）」とも称される。現在は不知森神社（しらずもりじんじゃ）の一角のみ立ち入りができる。

With regards to IME comments, apologies, I meant "you can't type "やぶしらず" and get the right kanji from IME".  However, my Mac does this fine actually...

Speaking of, is there syntax to mark that 八幡の不知藪 has an irregular reading, even though the main entry does not?[gikun]

When I saw this entry, I was suspicious that there was something missing in the entry, and that 八幡の不知藪 might be pronounced differently(it seems that it is not).

Top 10 N-grams 
八幡の藪	1899	  
八幡の藪知らず	1514

Top 10 N-grams Lookup for 八幡の薮 (Frequency Order)
八幡の薮	118	  
八幡の薮知らず	82	  
八幡の薮不知	25

All this editing, I didn't even notice that the wrong kanji is in the primary term.　薮→藪. 

I see limited evidence of 薮 to refer to the labrynth, but just to play games with us, the title of the pop/rock song uses the other kanji. Song post-dates the n-gram corpus though.  If we're not giving the song as a gloss, I don't think we need the kanji for that.

In general, in spite of the somewhat high occurrences, I suspect that 薮 is a typo.  Since you can't type ふしらず to get those kanji, you have to improvise when typing, and people who aren't certain may choose randomly.  A handful of pages I checked with 薮 somewhere had 藪 elsewhere.  Since the wikipedia article exclusively uses 藪, it's the name of a place and the map entries use 藪, and all of the cited authors used 藪, I'm marking the other form as [sK] and treating it like an IME error.　

You can see the same IME errors for the slightly different  籔 (bamboo radical), but that's not the name of a pop-song so I didn't add it. Google auto-corrects all of these if you search for them anyway.

@@ -5 +5 @@
-<keb>八幡の薮知らず</keb>
+<keb>八幡の藪知らず</keb>
@@ -8,0 +9,8 @@
+</k_ele>
+<k_ele>
+<keb>八幡の薮知らず</keb>
+<ke_inf>&sK;</ke_inf>
+</k_ele>
+<k_ele>
+<keb>八幡の薮不知</keb>
+<ke_inf>&sK;</ke_inf>

Interesting. Most hits are for the Chiba grove.

@@ -24,2 +24,2 @@
-<gloss>the feeling of being lost</gloss>
-<gloss>the feeling of being in a place where you cannot find a way out</gloss>
+<gloss>feeling of being lost</gloss>
+<gloss>feeling of being in a place where you cannot find a way out</gloss>

デジタル大辞泉「八幡の藪知らず」の解説
八幡やわたの藪やぶ知しらず
《千葉県市川市八幡にあった竹藪は、一度入ると出口がわからなくなるといわれたところから》出口がわからないこと。また、迷うことのたとえ。八幡やわた知らず。

https://kotobank.jp/word/八幡の藪知らず-649965
(千葉県市川市八幡に、迷いこんだら出られないといわれた「八幡の藪知らず」と呼ばれる藪があったところからいう) はいると出口のわからない藪。はいり込むと出口のわからないこと、迷うことをたとえていう。

「一度入ったら出てこられない、入れば必ず祟られる」という禁足地である。
https://www.pasonisan.com/rvw_trip/15-05yawatano-yabusirazu.html

八幡の藪知らず
https://ja.wikipedia.org/wiki/八幡の藪知らず
慣用句
伝承が有名になったため、「八幡の藪知らず」は「入ったら出られない藪や迷路」の総称となった。それが更に転じて「道に迷うこと」「出口のわからないこと」を「八幡の藪知らず」「やわたしらず」と言うようになった[注釈 3]。

================

Pre-1930s Japanese Text References:

https://kotobank.jp/word/八幡の藪知らず-649965
※虞美人草（1907）〈夏目漱石〉一六「何が何だか分りやしない。丸で八幡(ヤハタ)の藪不知(ヤブシラズ)へ這入った様なものだ」

1925 二葉亭追録 内田魯庵
https://www.aozora.gr.jp/cards/000165/files/49574_43497.html
...結局は出口のない八幡(やわた)知しらずへ踏込んだと同じく一つ処をドウドウ廻めぐりするより外はなくなる。

================================
Even though I can't find examples of this term being used as a synonym for labyrinth, I have found references indicating that this is so...
“迷宮”の代名詞として使われる八幡の藪知らず（不知八幡森）であるが、国道14号線に面し、市川市役所の斜め向かいにある。
https://japanmystery.com/chiba/yawatayabu.html

Note: This is a J->E dictionary. Also, it only pertains to the abbreviated 八幡知らず, not this full entry.
https://ejje.weblio.jp/content/lab・y・rinth
斎藤和英大辞典での「lab・y・rinth」の英訳
labyrinth
八幡知らず；迷宮

========================

八幡知らずの森 20-year old playing card. Shows popularity of the legend (again, doesn't exactly match this entry)
https://jp.mercari.com/item/m29727009225

「一度入ったら出てこられない、入れば必ず祟られる」
This was a very mysterious entry as listed. 八幡の薮知らず = "labyrinth/maze". So I went to figure out what this was.
First observation when googling was that the primary, overwhelming use of "八幡の薮知らず" online is to explicitly references a shrine/bamboo grove in Chiba.  The grove is associated with a legend, but the expression almost never appears outside of discussions of the actual shrine.

It looks like the there are legends surrounding the bamboo grove that are maybe well-enough-known that one could *possibly* drop 八幡の薮知らず or 八幡知らず[の森] in as a substitute for a labyrinth one cannot escape.  

Looking at the dictionary entries, in addition to being such an exemplar of a well-known labyrinth, this looks to also be a figurative expression to show the "feeling of being lost" or of being unable to find an exit. 

There is a song by R-Shitei (R指定) 2014 by the name "八幡の藪知らず", and the lyrics do at least seem to allude to the legend: "もう二度と抜け出せない奈落へ"
https://lyricstranslate.com/en/r-shitei-yawata-no-yabu-shirazu-lyrics.html

There is a line in a Natsumi Soseki novel from 1907 (see references) 丸で八幡の藪不知へ這入った様なものだ.  I wouldn't be shocked if he popularized the expression, however popular it might have ever been.

I just contributed something that related to the Yasukuni Shrine.  I am sure this shrine, now properly named 不知森神社 "Shirazumori Shrine", is not ordinarily notable enough to get an entry in jmdictdb, but it seems to make the entry more useful to say at least something about the legend if this term is going to be included.

Dictionary suggests that "藪知らず" could stand alone as an expression, but I can't find any standalone references to that either that do not reference the shrine.

n-grams:
藪知らず	1811
八幡の藪知らず	1514
やわたしらず	47
八幡知らず	44

Wow, among the many explicit shrine references, I actually found a Japanese person explicitly say they had no idea it carried this meaning (迷路):
https://twitter.com/mielune8282/status/1244838037512548353
息子が目の前で迷路で遊んでて降ってきちゃった…。
迷路は英語で”maze”、
迷路を彷徨うならば、a-maze-ing …amazing!!!!
人生はまさに素晴らしいってことか！
********ちなみに、迷路の別名が「八幡知らず」とは知らなかった…。*********
神さま、そのまんまやん…。

@@ -15,0 +16 @@
+<misc>&rare;</misc>
@@ -17,0 +19,11 @@
+</sense>
+<sense>
+<pos>&exp;</pos>
+<pos>&n;</pos>
+<misc>&rare;</misc>
+<gloss>the feeling of being lost</gloss>
+<gloss>the feeling of being in a place where you cannot find a way out</gloss>
+</sense>
+<sense>
+<pos>&n;</pos>
+<gloss>popular name for a bamboo grove in Chiba, famous for the legend that once you enter you can never leave (original meaning)</gloss>

@@ -13,0 +14 @@
+<pos>&exp;</pos>