Creating time base errors for testing TBCs?
 

Wondering if there's a process that produces the "bad" timebase errors for purposes of testing various TBCs and capture cards to see how likely they are to drop frames or lose sync altogether. My guess is that this would involve tapping or slowing down different parts of the transport mechanism of the recording VCR, or possibly even the use of magnets somehow, but I'd like to get more specifics on how that would be done.

At the same time, I'm not trying to create alignment issues haha.

Also, what's the best way to test for AGC issues that some cards are probe to have (automatic gain control)?