Mp4Box is failing to merge files with one I encoded

[Cyber Akuma]

My camera is hard-coded to split files at the 4GB mark even if the filesystem on the SDcard I am using can handle files over 4GB.

Ok, fair enough, it's a few seconds of extra work but I can always use MP4BOX to just merge them. And normally this would work, but during one of my recordings I have a 10 second gap near the end. It looks horrible to just merge them like that with the cut, and re-encoding an hour long video just to add a quick transition in the last minute would normally not be worth it, but I lucked out in that it had just started a new file past the previous 4GB mark when the cut happened, so I just have to add a transition between a 15 second and 1 minute file.

I wrote a simple AviSynth script to add a transition and then tried to use MP4BOX to merge them, but now it's not working. MP4BOX does not seem to like the clip I encoded as it's finding something (I honestly have no idea what) incompatible with it, and fails to properly merge the video. It tosses the warning "No suitable destination track found - creating new one (type vide)" and spits out a file that will not play. This only occurs when I attempt to add the encoded file in the mix, it has no issues merging all the original untouched files.

I am not sure what kind of information I am even supposed to provide to try to help with this.

Here is my AviSynth script:

Mov1=FFmpegSource2("video1.mp4", atrack=-1)
Mov2=FFmpegSource2("video2.mp4", atrack=-1)

Eff1=TransRipple(Mov1,Mov2,24,20,8)

FullMov = Eff1

ConvertToYV12(FullMov)

And what data MPC-HC reports for one of the original files:
https://pastebin.com/KMwqpxFv


As well as what I encoded:
https://pastebin.com/ZpvZ3pSL


I honestly do not see any difference, so I have no idea what MP4BOX is complaining about.

Does anyone have any suggestions what I can look into that could be causing this issue with MP4BOX failing to merge the files?