So I have found two things.
- I had it set to not pause on unfocus during previews, which is why it wasn't suspending when tabbing out.
- While messing with things, I found that it wasn't the wait action at all, but rather the the audio itself.
The audio lags behind if the computer is experiencing lag. This breaks the timings, because the audio ends early.
This also occurs if the game resumes after pausing.
I'm still unsure of how to fix the audio itself breaking, but I can now say it's not the wait action.