Ok, one step back...
1) You are indeed on Windows?
64 bit?
Intel (or AMD) / as opposed to ARM.
Your Lazaruse is 2.0.10 or .12 ?
According to your sig Fpc 3.2.0
I am testing 3.2.2 / and have previously had 3.0.4 / never done 3.2.0
2) Lets confirm, this is about running under the debugger?
designing has no issues? (afaik PasLibVlc does not load vlc at designtime)
"Run without debugger" should also be fine?
3) More details when the problems happen?
Is the error are (dramatic) slowdown? a freeze? a crash? a ....?
Does your app - when started - immediately start playing a video?
When does the error happen? (startup, when you play/stop/seek a video?)
Does the main form show?
When using gdb, open the "Debug output" (not "console output") (either view > debug windows / or view > ide internals).
Not yet important what the output is (unless is say big and fat "error").
But how much output is made while the problem happens?
(Just to see how much gdb has to deal with)
4) Does the issue happen with the examples in PasLibVlc? (DemoPasLibVlc)
Try different videos mp4 vs avi. (more important diff codec)
Bit of background...
From what I can tell a PasLibVlc project start quite a few threads.
Depending on how often one of them terminates and/or is newly started, this can cause extra event in the debugger. That can cost a few millisecs (if loading symbols is off). Not a dramatic amount of time, but enough to change timing as perceived by vlc.
If vlc's thread sync is vulnerable to timing (pure guessing... hypothetical) then that can cause freezing.
Check in the breakpoint window, that you do not have unwanted breakpoints.