The sticky piston, while lying on its side (only while facing positively on the Z axis) has a broken texture on the top. Not using a texture pack of any sort, not even the beta textures.
May be related - This screenshot was taken while running latest version of the official bedrock server software.
This still does occur in the regular game, however, with the server software offline.
Thank you for your report!
However, this issue is a Duplicate of MCPE-38053.
If you have additional information, please add it to that report.
Please search before reporting, as it's likely that one exists already.
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