Scataphagos,
Did buy a 10 TB Toshiba last week & it works with this 12 year old Dell T-7500. In fact it works with 6 TB + 10 TB totaling 16 TB. Just wanted to let everyone know.
Just curious, could that be a culprit ? Will take 10 TB out & see if problem persist.
What can be the culprit? Virtually anything. I once had an issue where I started out with a RAM test... passed as "OK". I eventually swapped out everything except the MOBO and still couldn't get it. Turned out to the RAM... even though a RAM test had tested OK. Waaay aggravating.
I am recommending to you my true and tested method. Just spray the crap out of the problematic contact and it will be OK. In my case, it's the RJ45.
My area is very humid.