Here is a proposal to copy data from the APE tag into the ID3v2 tag.
1. Create a group of actions ...
Actionsgroup "Test_2007#20070316.Move mp3gain from APE to ID3"[#0]
T=5
F=NEW_REPLAYGAIN_ALBUM_GAIN
1=%REPLAYGAIN_ALBUM_GAIN%
[#1]
T=5
F=NEW_REPLAYGAIN_ALBUM_PEAK
1=%REPLAYGAIN_ALBUM_PEAK%
[#2]
T=5
F=NEW_REPLAYGAIN_TRACK_GAIN
1=%REPLAYGAIN_TRACK_GAIN%
[#3]
T=5
F=NEW_REPLAYGAIN_TRACK_PEAK
1=%REPLAYGAIN_TRACK_PEAK%
2. Change Options ... Set Mp3tag to ... read APE ... write ID3v2.
3. Press [F5] to update the listview.
Read ReplayGain values from tag APE and write these values to tag ID3v2 ...
by applying the actionsgroup from step 1.
4. Change Options ... set Mp3tag to ... read ID3v2 ... write ID3v2.
5. Press [F5] to update the listview.
Read values from tag ID3v2.
Check the result.
If that works, then try it again with the correct fieldnames ...
(Change "F=..." from "NEW_REPLAYGAIN_..." to "REPLAYGAIN_...")
If that works, then apply it to the other APE tagged files too.
See also ...
Converting APE to ID3 ?
DD.20160304.1924.CET, DD.20160304.2054.CET