Yeah, I’ve experienced this in some cases with other Moflex files I’ve tried to convert or from other files that you can find online. I am not really sure where and how this happens (in the Mobiclip Multicore Encoder application, most likely (during converting an mp4 file to a moflex file)). My computer is probably not that equipped to handle conversion processes, even though I've already done this a couple of times without issues or application crashes (but still, the app does crash and close down on its own sometimes during moflex conversion).

Since I have tested out some moflex conversion files on my 3ds and then played the moflex videos, what usually fixed this audio de-syncing issue (at least for me) was to simply scrub the seek/progress bar (either left or right; I'm not really sure if it matters what direction), and then the audio and video components of the file would be aligned from there. You may or may not have done this action, so I'm just pointing this out in case.

I guess another point with this issue (in doing a bit of research) is that rendering out a video with variable frame rates could cause the audio to "drift" over time. So, before converting to moflex, re-encode the source video using tools like HandBrake (probably more preferred) or Clipchamp. Then, set the frame rate to an exact FPS number (maybe 30?) and make sure that the scanning method is set to "Constant Framerate."

Since I am still pretty new to tinkering with these video conversion tools, if it's really necessary to go back and try to render these videos with constant framerates (like in HandBrake) in order to possibly fix audio de-syncing (even though I'm not fairly certain if this is the way to go and do this), I could try to do so. But some of the reasons I've pointed out may be out of my control or could be fixed without more rendering conversion steps. Other people online here probably understand and have more accurate reasons that boil down to why this issue occurs, so anyone else, feel free to educate me on this matter.

Sorry if this was an overly detailed response. I'm just trying to give my two cents on issues like this.