HI I know it's lag for sure. I play Shor in KBPs (kilobytes per second) no fun. This usually happens with lag (my given Internet) another reason, why are you in a hurry to repair doors and walls? Is there no enemy? If no enemy, please slow down. These are the 2 situations that will cause the error above hmm if you go outside of cyrodill. That fixes it. Then yes there is lag issues. What is your connection like? Is campaign very popular.

I'm guessing your pc, due to saying add ons. I unsure if you have /reloadui as option to clean the ui? Usually fixes bugs and clear logs. Type /reloadui in chat box. If not work, try deleting non main quests (main story can't delete, not allowed to) try this though, it's an old fix, from ages past. It's pain to, but try do game repair via in game on pc. (have to re-download from repair option via in game) do this last resort.

I thought about the lag thing immediately and even thought, that I got booted, but abilities worked aswell as weapon swap. I could not repair at other keeps either, anything else worked fine. Also there were some issues with flaming oil, while ballistas for example worked.

Something tells me, we had this pattern before...

Oh and by the way: The amount at which the repair kits stopped working was always not stackable with others I bought to make sure, it wasn't lag. So I always had two different stacks, as if they somehow became different type of items.