When you execute a maneuver node and the current stage has not yet been burned at all, MJ throttles up and then back down real quick in some apparent test of thrust or something. In RO this means you lose an engine ignition which is bad.

This only happens in the specific situation of a fresh unused stage. One that has not been burned at all.

To reproduce just stage into a fresh stage but don't start the engine up at all, then execute a node.