When launching sky-high piston lift without riding it, above clouds (y>=127) piston which is pushed by another piston when retracts leave ghost...
This never happened for version <= 1.8.9
it looks like some kind of optimization bug introduced in 1.9
Environment
Launcher 1.6.59, JAVA (embedded in MC) 1.8.0_25 64bit
windows 10 pro 64bit pl, windows 7 pro sp1 64bit pl
This is a probably the same bug as MC-96219.
You might want to watch this video for somewhat of an explanation: https://www.youtube.com/watch?v=ox3lAl2rXpM
(The bug is marked as 'fixed, fix version: 1.9.1+'. This implies the bug will soon be fixed.)