Yes that's the clutch slipping in the gearbox due to over - torque on the drive. - so you don't overload the electronics and blow it. You could try bonding the clutch plates together with cyanoacrylate (superglue) to stop this but you will be putting your MFU at risk with this mod. - a lot of guys do this. It's actually a very sensible feature. You wont see it on the metal gearboxes so this is a real risk - especially for like for like gear ratio's. So a hot motor in a fast ratio metal gearbox will increase the risk which is why you probably need to upgrade the electronics as well - hey ho!!!!

Cheers

CaptB