I must admit I am puzzled why reverting https://github.com/silvanmelchior/RPi_Cam_Web_Interface
gives you a working version of raspimjpeg because the compiled binary changes only started to be tracked when this GitHub was created. I know that myself and a few others experienced the poor Night mode after Silvanmelchoir's first raspimjpeg update (8th March) since January, which would have been overwritten to us on his server before it was tracked in GitHub.
Also looking at the source code, the change from v2.0 to v3.0 happened when time-lapse was implemented, and I certainly still have Night mode issues at this version as it's what I'm running at the moment.
Perhaps things have become even more worse with the new binary at v3.1 and v3.2 that I haven't seen, and in which case just ignore my mumblings above.
Anyway, I've been unable to test the old, newly compiled raspimjpeg code this evening because my remote Pi with IR failed to reboot for some reason, so have to check it in the morning...
It's a shame there's no obvious way to find out why Night mode is so poor now.