It is usually difficult (not to mention unfair) to apply new conditions to a contract retrospectively.
I would have thought that the best way forward is to simply write any new requirements into the
next contract.
All that extra stuff will end up costing you more, of course, especially if the contractor needs to be worrying about protecting himself the whole time.
As I say, what matters is the condition of the kit. If you can't judge that for yourself, then you may need to consider calling in a third party to examine it (spot checks, whatever) on your behalf. More expense!
What sort of equipment are we talking about here, by the way?
Meanwhile, the fact that a tech had to check up on something or other sounds to me like a
good sign. Honesty, due diligence
etc. ... rather than simply bluffing his way through!
... but at the moment we could not show them anything.
Show them the kit itself! And if they know what it is they are are looking at, and it's in good shape, then it's Game, Set, and Match!
