no image upload from specific computer

I have several WordPress websites, running 5.7.2 and 5.8 and different themes. Suddenly I cannot upload to any of them any more via the WordPress media library. I tried different browsers, emptying caches and disabling all plugins. My computer runs Windows 10. I tried with another computer (Windows 7), and from this one there are no problems. I can also upload via 4G and via the CPanel File Manager.

The error notice I get is the following: Post-processing of the image likely failed because the server is busy or does not have enough resources. Uploading a smaller image may help. Suggested maximum size is 2500 pixels. The files I tried to upload were not large, however I increased the permissible file size to 100MB, but this also had no effect. There are no other error messages.

I contacted the host who said they could not see any problem and had no problem uploading. We were asked to empty our cache and to ask our ISP to empty theirs. The ISP said they did not have a cache, internet connections were direct. I did not change any settings on my computer, not sure what else to try. Does anyone have an idea what the problem might be?

Thanks!!