slime block becomes "invisible" for a short amount of time

i was trying to create a redstone contraption to push a slime block up with a sticky piston (activated by tripwire) the contraption worked not like i intended but that's not the point, when i was above the the sticky piston activating it with the tripwire the slimeblock was pushed up but it would vanish and so would the sticky piston head only for a short time, not that big of a deal but i thought you guys should know.

ill try to explain how to reproduce:
1. place sticky piston face up with a slimeblock on top
2. build 2 towers up with a tripwire connecting them
3. attach the trip wire to the piston with redstone
4. test the contraption a few times hopefully you will see what happens and fix it, thanks