[macOS High Sierra] Slight Movement Freeze Upon Beginning To Click

[CJ Burkey]

That title is very strange sounding, I know, but that's only because the problem is very strange. Basically, every time I begin to click my mouse (the left button is pressed down), the game will appear to freeze for about 200-400 milliseconds. I say appear to freeze because the game still runs, and animations and stuff continue for this period of frozen time. It's just that the player freezes in place and the mouse locks.
I've been playing on a TTT server, I'm the only one who's experiencing this, running the latest released GMod version on Steam, and running macOS High Sierra 10.13.2.
I have tried complete game reinstalls, but those do not fix it. If you need any more information, I'll provide it to the best of my ability, thank you in advance for your help.