Looking through the 12.2 changes to refresh my memory, I can't see any that look likely to have affected this.
Sometimes it's just a coincidence, and another component's change or a Windows update was waiting, pending the reboot done for Opus, so two different things get updated at the same time. Sometimes rebooting again fixes things if the problem was caused by the timing of different components starting up in parallel during the previous boot.
Occasionally just moving our code around in memory slightly, due to small changes to the code, can trigger or cure issues where another component has a bug which is harmless if a particular memory address is not being used but causes problems if it is. (That kind of thing is unlikely to make things slow down rather than not work at all, though.)
Not always, but a lot of the time when a problem seems to come from a particular update, it turns out to still be there if the previous version is reinstalled. I can upload the 12.1 installer if needed, but it's best to check for a slow shell extension first.
It may also be worth looking at what is in the Open With menu. Perhaps something in there is pointing to a program that has its icon or exe file pointing at a network drive that no longer exists? That could slow things down considerably when displaying the menu. The debugging steps can tell you if that is worth investigating. You'll see something like this in the output:
If there's a large amount of time between "Open-With Menu: Building" and "Open-With Menu: Done" then the problem may be in there. But the delay could come from one of the other parts, too. The debug output will hopefully point in a good direction to look.