You may want to turn the power off and check the wires in the outlet that the Microwave plugs into to make sure they are tight. You may also want to do the same at the circuit breaker for that outlet.
The draw of the convection oven is quite a bit and if the wires are loose, it could be heating up the connections when on for a prolonged period of time and causing your problem.
2005 Safari Cheetah 38PDQ - 2009 Ford Flex
Me (Gatogonow), The Boss (DW), Honey Bunny, Maggie May and Mollie Kay (The Gatos)!