Under certain conditions (which I did not try to determine precisely because it happens rarely and without any apparent link with constraints specific to the block) a "redstone" signal on of any intensity is not transmitted by a block.

This seems to happen on a random block each time the world opens and seems to affect the same blocks regularly.

The error persists on the block until the world closes or the placement / movement of a nearby block (~ ± 5 blocks around in each dimension), the modification of the incoming signal has no impact on the bug. Found only on "quartz blocks".