Weirdest bug I've ever seen - Repeater getting pulsed without a single reason

When standing ON TOP of the cobblestone in the picture, your coordinates are:
x: 849
y: 16
z: 1743
The repeater is facing f: 3

What I expect to happen when I switch the lever: The bottom redstone will turn on, and nothing else will happen.
What happens: The repeater turns on as if it received a pulse.

This does not happen elsewhere, where I tested at least.

Repeaters on other sides of the block will not do anything.

Removing the block which is cutting the 2 pieces of dust, or either of the 2 pieces of dust, will result in the bug no longer happening.