Splitting MP4 and wonky thumbnails

[Scotchtape]

Hi there, i'm having to split some AVC MP4 files into 2 parts for online streaming and having a problem with the thumbnails in the second part. The thumbnail selections for that part on any file seem to all be pure grey or a sort of smudged grey once uploaded. The first part thumbnails are all fine, it's only the second and other than that they seem to work ok whether it be online streaming, on my PC, on my tablet etc.

Here's a pic to show what i mean https://forum.videohelp.com/images/imgfiles/hB8SCPR.png

They are files that were all encoded with MEGUI a while back and work perfectly, my only issue is the thumbnails after they are split.

I've tried YAMB, My MP4box GUI, going to Tools > Muxer MP4 muxer in MEGUI and splitting there, even tried doing fresh encodes and have MEGUI split automatically at the end. They all turn out the same with the grey thumbnails for the second part once uploaded for streaming.

I'd appreciate any help on the cause and hopefully a fix if possibly.

[Budman1]

Is the image from the site itself? Since the first half shows okay and the second one doesn't, I'd use AtomicParsley "video.mp4" -T to compare the atoms. I used MP4BoxGUI and used the SPLIT tab to split on MB boundary and mine both had thumbnails and image at
my GoDaddy site.

[Scotchtape]

Yeah that image is from the site, they give 6 thumbnails to choose from after upload and with these split ones usually all 6 or occasionally 5 of the 6 have either blank grey or the weirdness you saw in the pic i posted.