I would expect that at 70% or maybe even 90%, but 99% isopropyl should absolutely not leave a residue behind.

How long ago did you get iso in there? If it was really recent, there’s a chance it may evaporate and be good as new. If it’s been a while, take solace in knowing it probably won’t get worse, at least.

“I frequently interface with idiots, so I don’t feel it would be safe for you to have full control over the hardware you own.”