Xperia Z5
The extended/powered pistons more likely to "reactivate (as if they were powered off then on)" when you load a world.
How to produce:
Start a world
Place few pistons
Connect them to any continuous redstone signal
They should extend
Leave the world
Enter again
You'll here the piston extension sound and the pistons being re powered again
Thank you for your report. This issue was, however, submitted earlier as MCPE-17464. Please perform a search next time to make sure your bug hasn't already been reported. The parent issue can easily be found by searching for "mcpe unresolved piston retract".