As I posted below, I am having a problem with the pistons block. After placing a block on one piston, you can no longer place any blocks on any other pistons. In other words, 1 working piston per game. I noticed this after downloading ver 1.9.7. The same problem occurs in ver 1.9.6.
However, the problem does NOT occur in ver 1.9.5.
So pistons stopped working in version 1.9.6. FYI.