If a garage door is powered by multiple redstone sources, and one of them is removed, the door closes, even though it's supposed to stay open (because there are other sources powering it). Causing a block update near the door will re-open it. Tested in the latest version (v3.3.7 DEV) with only NEI and WAILA installed as well.

Interesting. Will investigate.

It's likely an issue with the onNeighborBlockChange function in BlockCarpentersGarageDoor - specifically, it doesn't handle the garage door spanning multiple blocks horizontally. Perhaps keeping a count of powered blocks would fix it.

Indeed it seems I should take the power state of all doors into account. I will issue a fix soon.