[odorousrex]

You don't fix them.

You bring in an entirely new machine, and the old one is securely destroyed.

[jandrese]

Oh yeah, like getting a new machine through purchasing and certified for the SCIF is a walk in the park...

[nine_k]

You have a stock of prepared, vetted replacement machines.

You can replenish it slowly after you have just handed over a replacement.