I would personally doubt that it's dust - as the Fusion is fairly well "sealed" when closed. I always cover the keyboard when not in use - to minimise any airbourne stuff . . . .
Perhaps the previous owner didn't . . . ?
I suppose I've opened mine as many as 10 times, with Memory upgrades and various experiments with drives etc... It gets less harrowing as you get familiar with doing it - ESPECIALLY closing it.
Do you think its been opened before you got it?
Look for bits of glue that hold bits of wiring loom in place - that are no longer stuck down . . . Screw heads or hole-surrounds showing "wear".
These need not be cause for concern per se - more trying to build up a "history".
Has the memory been upgraded? To my knowledge, Fusions were always unexpanded when new . . .
With CAREFUL propping of the "lid" it should be possible to power the Fusion up with the lid opened and moved to the rear slightly. (Scatter-cushions" or towels are good for this - they are mouldable AND non-conductive

)
This HAS TO BE at your own risk . . . . There is MAINS in the vicinity of the PSU and possibly elsewhere . . . . DO be careful - or enlist some "informed" help.
Try the keys in this state. Has the problem disappeared? If YES, then the problem is most likely to do with the precise replacement of the lid . . . .
If NO, then you could try using a Dustoff® Aerosol on the contacts and see if that helps.
Take a CRITICAL look at the contacts/springs etc in the area of the problem . . . are there any that look "different" to the majority. The Keybed is a respected "make" and I'm sure spares CAN be had if required . . .
Check the innermost ends of the keys (i.e. the contact end) to see if any tiny pieces are broken off.
New keys are easy to source, I believe, if required.
I think the Keybed has TWO feeds to the mobo, one for upper keys, one for lower keys . . . .
Identify the lower one and try unplugging and replugging one (or both) ends, if you can access them.
I THINK there is a diagnostic routine that can be run, that goes through ALL the keys/buttons/switches - but be careful to avoid the disk related ones - they CAN erase the HD . . . .
If any of these give you an error code in the display - then that code might point to the problem AREA.
There is a list of "known" codes somewhere in here - and what they mean (in plain terms). I think <Jesse> looks after it.
Hopefully it won't get to that.
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