This is super strange. I've tried reproducing on my end and have been unable to. A couple of questions:
Is it happening in only one drawing or is it happening in every drawing?
Have you tried closing/syncing the drawing, then force-quitting Fresco, restarting your device, and relaunching the app?
If this is happening with every drawing and you've already tried force-quitting, please message me through Fresco's Report A Bug link (tap the gear icon in the upper nav of the Home screen then from the App Settings menu tap Help > Support > Report A Bug).
You don't have to resend the video just let me know that you posted here.