I just completed renovating Maus and the things I could not do I left for last. Namely can't assemble:

• driver periscope
  
• two radios
  
• radio connector
  
• two extinguishers
  
• hull external - fuel hose

I remember when in disassembly mode at the start I was able to remove these parts (I don't remember the hose, but the rest I do). After some time I was able to see this 'hologram' on which you right-click to install a module, but they're gone now. I noticed I have to switch between assembly and disassembly mode for some holograms to appear again, as they disappear sometimes, reason unknown. I could live with pressing 2 and 1 on the keyboard in order to do so, but now that I can't assemble some parts I am simply mad.

I saved the game two or three times during this renovation. I thought maybe if I go to the test track and back something will change, so I filled fluids and went there, but I can't start engine because 'fuel not filled', despite it being at 100%. I suppose it could have to do with absence of a fuel hose, but I can't be sure. I know nothing about tanks' inner workings after all.