It's been bugging me for a while, but I just changed my computer and now have a really powerful machine. I thought it would resolve the issue, but apparently not.
So here goes.

Amost all the time, when I want to batch export PNGs from files, it fails (see screenshot) it can happen with a whole selection of files, but also with just one. I noticed that whenever the files are on the biggest side, it will get worse. The error report says "unsupported format.
The same file(s) will have no issue being exported as TIFFs, or JPEGs, just not the PNGs. I managed to export 80-ish very high res files (think 6000x8000) in TIFF without any serious slowing down, even on my old computer.

Things that I found can help:
Compact the cache, although I have more than sufficient space in there (see screenshot). In some instances I had to compact the cache repeatedly, no sure if that even helped or it was just coincidence. Sometimes exporting one by one can help, but not always, but that negates the whole automation aspect. After all, I can do that in Photoshop.

Step I resorted to use:
- use the Image processor pro, although it's still a pain to install on newer computers
-Open my files in ACR - if the original file format permits it - and export from ACR. No ideal.

I never had any issues with the ACR export.

It's been going on many years. My new computer is Ryzen 9, 128 Gb RAM, 2x 4TB SSD, with a 16GB GE Force RTX 4060. So I don't think it's a RAM or Disk issue.

I am aware that there are others bug reports but they are all quite old, and wanted to put that to the devs attention.

Thank you!