It's difficult to guess what might have changed from our end, unless it was something in the Opus update that you mentioned. (That's unlikely, but you could try reinstalling 10.5.3.0 to check that possibility.)
In the realms of guesswork, these two guides may have some useful ideas on what to look into:
[ul][li]Crash, exit or high CPU usage when viewing certain directories[/li]
[li]General slowdown or instability investigation steps[/li][/ul]