So even if there is no existing dopus.exe on the Task Manager Details tab, you can't restart Opus until you reboot the machine?
That points to something blocking Opus from running, where that thing starts later than Opus after a reboot. Or possibly an OS component is failing at some point after reboot.
We might be able to see where it's failing if, with dopus.exe not running, you capture a Process Monitor log of what happens when you try to run dopus.exe and it fails. Here's how to make the log:
Also, try whitelisting dopus.exe in your antivirus, especially if you are using Defender (which has been terrible lately, and requires editing two separate whitelists: One for Antivirus Scanner, and another for Protected Folders, both of which can block Opus and other programs).