Exporting sequence directly from Media Encoder gives error on some frames "media offline"

I'm having issues in Media Encoder exporting an image sequence. I've seen other forum topics that are related to this but *are not the same*. I do not have a Premiere Pro sequence, this is for a sequence directly added to Encoder by going to "add source" and selecting the first image in the sequence.

I've done the following to debug the issue:

1) restarted computer

2) tried images in a different folder

3) cleared ME's cache

4) turned off the setting for "import sequences manually".

The files are all in the same folder on my C drive. There is nothing else accessing the files at the same time. The system is brand new and extremely powerful, 64gb ram, Intel Ultra9 processor, RTX4070 GPU.