Sky Demon

just mentioning. a game tick is 1/20 of a second. a redstone tick is 1/10 of a second, anyway It does seem to happen how you say it should. Perhaps high level regeneration lowers/removes your damage invincibility time to allow you to take damage every single tick?

I would like this to be fixed but some maps use this as a balancing mechanic. For example super powerful signs that are amazing weapons until you accidentally place them. Perhaps making "normal" enchantments act this way. However add a method to attach tags to a block/item that are persistent when the item is placed and broken. Maybe a compound tag named "persistentData" and any tags inside it will be retained when the block is placed and will apply to the item each time it is broken.

Check if you are crouching when it happens. In the mod redpower there are small blocks that are placed differently where you place it on the block. But if you crouch the preview shows correctly but it places where your crosshair would be if yoy weren't crouching.