Plot hole: Professor Jones says they tried to borrow the cutting equipment a few weeks ago, but Mr. Stevens says it was yesterday. One of them must be wrong...
Plot hole: Jo should know what the dematerialisation circuit looks like. She saw it in 'Terror of the Autons', 'The Three Doctors' and several other episodes.
Answer: TARDISes are generally available for properly authorised use on Gallifrey; they're not usually assigned to a particular Timelord on a long-term basis. The Doctor stole his when he left his homeworld.
Tailkinker ★