Command block is being destroyed when wither is created above the command block. The hardness of a command block is -1 which means wither shouldn't be destroying any block with hardness -1. I'm on Samsung Galaxy Tab 4
MCPE-20344
Command block bug (1.0.5.0)
Resolved
Duplicate
0
(Unassigned)
Unconfirmed
Tablet - Android - Other (Specify in description)
Android 4.4
1.0.5.0
Retrieved
Many bugs in 1.0.5.0 so maybe fail? Instead of -1 maybe it's 1