I did my research on the 1.15 bug fixes, and didn't find a fix about this particular bug. I think the issue lies within the piston block. The snow layers from the snowstorm sometimes resets the piston, and prevents it from retracting. I stumple upon this bug from time to time when I am using a flying machine that flies through snowstorms. I end up having to start the engine again, for it to continue. 

1. The flying machine flies perfect.
2. The flying machine enters a snowy biome / snowstorm
3. The flying machine suddenly stops after a while