I have a similar situation with a 5N2. It is a couple months out of warranty. I did not opt for DroboCare. Seemed expensive relative to cost of 5N2 and drives.
I have a Drobo Gen 2 and a Drobo FS, all still in operation with no issues.
All my Drobo’s act as local NAS archives.
The 5N2 was populated with 4 8TB Seagate and 1 5TB Seagate and mSata cache.
The Seagate drives were all from peeled USB3 drive enclosures.
Things were working fine for a year. It had been set for 2 drive failure protection.
Last week it indicated the 5TB drive needed to be replaced.
I went to Costco and got another 8TB backup drive, I formatted it, peeled it, and swapped it in where the 5TB had been. The Drobo initialized it and then began the rebuilding process. That finally completed in a day or so.
Then it started eating drives.
I exported the event log. So that can be seen. I also have the email alert messages.
The unit is turned off now.
I am not sure what I should do.