In my opinion, if your engine was not doing this on previous flights and began doing this recently, I would check fuel tank fuel line for hardness. Replace them every two years because they will harden and will not follow the fuel when rolling or inverted. Don't put the pickup too close to the back of the tank. Also check all of the lines for micro cracks. When engines quit during flat spin manuevers. that can be because of overheating. Putting in baffles solves this problem. If you do not baffle the engine, you will have to richen the engine more than usual to counteract the heating.