When you power a dropper or a dispenser from a solid block above with a Redstone strength of specifically 8 it only triggers the once after you have placed it. Then it doesn't work. But if you replace it it works once again then breaks once more.

In the picture attached the signs indicate what signal strength the Redstone above it has. The one with the 8 is the problem and as stated before only work once after placement the breaks

other Redstone components such as pistons and Redstone lamps works. And if you power it specifically directly to 8 it doesn't break

Update: After further investigation it isn't always on signal strength 8. But the problem still stands. but it seams random on which one breaks

Update 2: It seems to be every other one