Xperia Z5
I've been facing this issue since 0.15. in survival I have that "semi auto farm" that uses the water that's trapped between an extended piston head and a block to break the crops when I unpower the Pistons (so the water flows towards the crops) and when I go far away (so the chunk disappears) and when I go back I see that my planted crops has broke as if the water was flowing over them.
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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".