It sounds like you might be describing what is usually called “fret buzz”… like a quick loudish rattle when either not pressing down close enough to the fret / not pressing down hard enough / or lifting your finger off the fret too slowly (there are other factors but these seem to be common)
-
If that’s not quite what your describing then ignore what I write below and maybe try to describe it in another way to make it clearer if you like?
-
If that DOES sound like what you’re describing, then honestly don’t worry too much about it. I’m still fairly new myself and I’ve noticed it’s something that literally improves over time as you get more comfortable with playing. The good thing for early on is to be aware of what it is you’re doing that causes it so you can at least have it in your head that it’s something you can gradually correct as you go on.
A good bit of advice if you’re in the B2B course is to read the comments for each video and you’ll be surprised how many people ask about it, and how many times Josh has written out a new, human response to each one 
Muting is something that will likely take a longer time to get right so definitely keep trying but don’t let it frustrate you if you don’t nail it every time yet