[Pnguyen1028]

Now this is probably a question better suited for an audiologist or a dentist, but I figured I'll ask anyway. 
 
I recently purchased a pair of unique melody Merlin's and the fit has been bothering me since day 1. The right earpiece doesn't quite fit well but the left earpiece is perfect. This is a common occurrence with the custom iem process I'm well aware of. I'm looking to get the right earpiece redone and before I go get my impression, I'm curious about my particular situation.
 
I have a third class bite (underbite where my lower jaw protrudes past the upper). When I open my jaw, it also pops (dislocates?) on the right side. How does having a third class bite affect my open jaw impression compared to a regular bite? Is it a coincidence that the side that my jaw pops is the same side that the earpiece doesn't fit well?
 
Or in the end was the impression just bad and my bite has nothing to do with anything?
 
Any tips on what to do (how to hold my mouth open, how wide, etc) next time I get my impression?
 
Thanks.