Steps to reproduce:

[Step 1] Build a contraption like in the video powering the block diagonally above the dropper/dispenser through a repeter (does not work without the repeater, any delay works). 

[Step 2] Power the dispenser/dropper thus powering the repeater and block.

[Step 3] Place/remove blocks adjacent to the dropper/dispenser and make it activate again

Observed results:

The dropper/dispenser does not activate more than one time after being updated by placing/removing a nearby block when included in the redstine build.

Expected result:

The dropper/dispenser should activate every time it gets powered.

Video llink: Youtube video

Another video where you can see (I think) the same problem: Youtube video