Okey dokey... CC was the culprit. I dropped a sim I had made some time ago into Windenburg to use as my test sim, he couldn't order upgrade parts. Next I started a new game with the same sim but took off all his CC before dropping him into the game. He couldn't order upgrade parts either so I figured it must be a game bug. Until I started another new game but this time I took my CC folder completely out of my game files first. This sim could order upgrade parts just fine.
So, even though all my CC was showing up just fine in-game and there was seemingly no CAS issues or flickering etc etc... CC is still to blame. Lesson learnt, don't use CC when testing stuff out.
