Sounds like Sharp went all cheap and neglected to put a screen on the cool air intake. If I am understanding you, and I'm an etech myself, actual mosquitoes are finding a way inside the MW and accumulating between the electronic display and the front glass?
If that's the case, what I'd do is bite the bullet, remove the MW and glue nylon netting to any openings in the case. Then I'd spray bug spray all around inside the compartment, soaking into the wood, or find some other method of discouraging any flying bugs from entering.
OH! Just thought of something. Do you have one of those fancy schmancy RVs that has and exterior kitchen fan? I bet if you do that the door is ajar or broken or not closing right. Mine would snap open when I switched on the stove fan, and snap shut when I turned it off. If that is open without a strong airflow, bugs could get in that way. So check that.