Powering any type of block placed in the same way as slabs causes pulses though them.
The bug appears during tests on an updated redstoned elevator (original concept by minecraftpg5) on a first computer using java 64-bit.
The pulses go from the rising signal module to the decreasing one though adjacent blocks without any connection, at different heights but NOT at all ones.
The circuit as seen in the following pictures shows the same bug as the elevator.
The first one ("powered_redstone_repeater") is an instant screenshot when the circuit is running.
The second picture ("stable_state") shows the stable state of the circuit when openning the world on the second 32-bit computer.
Any try to turn on the clock again on the second environment causes a crash of the game.