exp not needed here.

@@ -16 +15,0 @@
-<pos>&exp;</pos>
@@ -27 +25,0 @@
-<pos>&exp;</pos>
@@ -34 +31,0 @@
-<pos>&exp;</pos>

正面に	672161	25.4%
まともに	1969712	74.5%
真面に	1117	0.0%
GG5, etc.

Moving the senses to match the examples. 真面に  is quite rare.

@@ -5 +5 @@
-<keb>真面に</keb>
+<keb>正面に</keb>
@@ -9,2 +9,2 @@
-<keb>正面に</keb>
-<ke_inf>&rK;</ke_inf>
+<keb>真面に</keb>
+<ke_inf>&sK;</ke_inf>
@@ -30,4 +30,2 @@
-<gloss>honestly</gloss>
-<gloss>decently</gloss>
-<gloss>seriously</gloss>
-<gloss>fairly</gloss>
+<gloss>properly</gloss>
+<gloss>normally</gloss>
@@ -39,2 +37,4 @@
-<gloss>properly</gloss>
-<gloss>normally</gloss>
+<gloss>honestly</gloss>
+<gloss>decently</gloss>
+<gloss>seriously</gloss>
+<gloss>fairly</gloss>

まともに動け	6844	100.0%
正面に動け	0	0.0%
真面に動け	0	0.0%

https://eow.alc.co.jp/search?q=まともにまともに頭が働く
think properly
think straight

まともに振る舞う
behave normally

まともに結婚している
be properly married

まともに英語が読めない
can barely read English

https://context.reverso.net/翻訳/日本語-英語/まともに
I couldn't live properly even at the lowest level as a human.
まともに生きられない

トムはいつまでたってもまともにフランス語喋れるようにはならないんじゃないかな。
I doubt that Tom will ever learn how to speak French properly.

Properly glosses (20):
https://context.reverso.net/翻訳/日本語-英語/まともに#properly

Other comments on [rK] and kanji at the main まとも entry.  Not sure if/how my suggested change here might apply there.

Saw this in the context of an old man who had finally taken a tumble and found himself bedridden.  今までまともに動けたほうが奇跡のです。 Someone's translation: "If anything, it's been a miracle I've been mobile till now". (ie. that his body had been able to move properly) 

Looking into eijiro and reverso, I see several examples of "physically working properly" or "not working normally".  While we have/had "properly" as a gloss in [1], it blends in with a bunch of words that connote morality, not (physical) functionality.

This sense is not at all obvious in the kokugos. sankoku just says 1: しょうめん 2: 真面目・本気.

I'm suggesting this edit because I couldn't understand what I was looking at with only the previous sense[2], and had to go looking for other resources.  (I wondered if he was talking about "having lived an upright and honest life" to that point).  I think a separate sense [3] will make this entry generally more comprehensible.

@@ -4,0 +5,4 @@
+<keb>真面に</keb>
+<ke_inf>&rK;</ke_inf>
+</k_ele>
+<k_ele>
@@ -5,0 +10 @@
+<ke_inf>&rK;</ke_inf>
@@ -28 +32,0 @@
-<gloss>properly</gloss>
@@ -30,0 +35,7 @@
+</sense>
+<sense>
+<pos>&exp;</pos>
+<pos>&adv;</pos>
+<misc>&uk;</misc>
+<gloss>properly</gloss>
+<gloss>normally</gloss>

gg5, wisdom

We need the second sense as well.

@@ -13 +13 @@
-<xref type="see" seq="1378040">正面・まとも・1</xref>
+<xref type="see" seq="1378040">まとも・1</xref>
@@ -14,0 +15 @@
+<gloss>right (in front)</gloss>
@@ -16 +17,2 @@
-<gloss>in front (of)</gloss>
+<gloss>straight (in the face)</gloss>
+<gloss>head-on</gloss>
@@ -17,0 +20,10 @@
+</sense>
+<sense>
+<pos>&exp;</pos>
+<pos>&adv;</pos>
+<misc>&uk;</misc>
+<gloss>honestly</gloss>
+<gloss>decently</gloss>
+<gloss>properly</gloss>
+<gloss>seriously</gloss>
+<gloss>fairly</gloss>

正面に	672161
まともに	1969712
GG5, 中辞典

Split from 正面 entry. I'll reindex the sentences.