While using a script button to automate the Find command, Opus' find thread crashed multiple times, but apparently only when multiple (at least 10 as a guess) folders were selected on the source tab.
I sent a mini-dump by e-mail in case the developers want to analyze and patch the issue.
The script button used in case you want to try to reproduce:
Find (by filter).dcf (2.9 KB)
(If needed, check this thread to understand what it does.)
I have modified the script to try to sidestep the issue and it appears to have worked.