All 200 desktops stopped connecting to the server at the same time with same Deadline exceeded error. I'm not sure if agent check in time would help. I will contact ESET support and ask for help if this repeats.
When you see permissions error while uninstalling agent,just reboot the PC and uninstall.
At this stage please use ESET uninstaller from safe mode to remove all the traces,reboot to normal mode and reinstall