I tried that. Nothing in the Kerbal's inventory, yet the bars go read. I have two ships docked with each other. I was able to place two thrusters on my ship but then after that it would not let me do more. I should mention that I also tried removing everything from the kerbals' inventory and that still didn't work.
Here is a pic
https://pvbi0-my.sharepoint.com/:i:/g/personal/gardei_pvbi_edu/EcgmHNuR7xlJmNZZlL4iFjsBHi00ndeC1Fy1Ray5ao-rdA?e=puAM7w