I felt similar experience trying to reorganize solar panels. turns out when you repair the slot, the item can no longer be removed until the slot goes down a bit in "failure" so at 99% I cannot take out a heating element, but if I go to bed get up and go get it in the morning at say 94% rather than repair slot, I can do it.
took me a while to figure it out. I was scrapping a hab to move to another one.
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