missing audio
 

lately I have been noticing that certain clips have missing audio usually somewhere in the middle.
Like a minute clip will have 30 seconds of no audio then it will resume like nothing happened.
I recaptured to make sure it wasn't a transit error, same result.

That said since I cleaned the heads a few times I haven't had that happened, but besides dirty heads is there anything else I shoot be looking at?

Thanks much!