Hi Blair
I have found the 1% building issue occurs if I do this (not fully tested - just going from memory)
Colonise a planet with 5 tac slots
Queue up a tac upgrade
Place a phase stabaliser
then click to build mines/trade ports etc...
Often the phase stabaliser is built to 1% and then its like the construction ship goes "Hang on a minute, there aren't actually enough slots ready for this, better go build something else...".
At this point, since it has actually been started, it could be blown up...