As of the beta versions of 1.16 and 1.15 if slime blocks are placed next to other bblocks, they don't launch players. The blocks beside maybe any movable blocks and even obsidion and bedrock. This breaks most of the slime block launch elevators. This was alright in 1.14 but now it isn't. It still launches players if nothing is beside the slime block.

I hope this gets fixed.