5D - Internal error and wrong drive being used for cache

I have a Drobo 5D that I have had since late 2013. All 5 bays have 3 TB WD Red Drives. Lately I started seeing message on my Mac that the Drobo was ‘not properly ejected’ after waking my Mac from sleep… but it would be connected and running. I caught it happen the other day while using my Mac (I wasn’t accessing data on the Drobo at the time) - but the Drobo just restarted for no apparent reason. Obviously causing the message 'not properly ejected message.
I went through the event logs on the Dashboard and there are messages with a red indicator that say “An internal error has been detected” and the very next message says the Drobo has been powered on. Otherwise all my data seems active and available… all drive lights are green, etc. Obviously I’m concerned, I have critical data on there (I do have backups) and need access and need to preserve the integrity of the data! Any help would be appreciated!
One other thing I saw in the event log… when it starts up it lists each drive in the event log… then it says the drive in Bay 5 is being used as a cache drive. But I have an mSATA SSD in the mSATA bay and it shows to be active and in good health? Why would it be assigning Drive 5 as a cache drive?
Dashboard at version 3.5.2
Firmware for Drobo is at 4.2.1
Connected via Thunderbolt 2 to a Late 2013 Mac Pro running Big Sur 11.2.2

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If you have the hardware available, you could always double-check the mSATA drive’s health, your Drobo will stay useable without it (if slower). Checking the cable (by substitution) might also yield results.

Main thing though is to step through thr FAQ for Big Sur, make certain nothing has been missed:
Frequently Asked Questions: macOS 11 Big Sur (drobo.com)

The mSATA issue was my error… drive 5 is the mSATA card, so that part is working fine.

But, I still get the occasional reboot of my Drobo 5D… just randomly it seems? So far, it hasn’t restarted while I’ve been writing data to it, but that may just be a matter of time. The event log show ‘internal error’. I did pull off the diagnostics - is there any advice as to where I might look in there for a cause of the errors and restarts?

As I noted above, the cache issue was my misreading the info panel.

But, I continue to get the random ‘Internal errors’ that cause the Drobo to restart. I replaced 3 (7 years old) of the 3TB drives in the Drobo with some used ones that had been in a friends Drobo - his were several years newer than mine. The internal errors got less frequent - I hadn’t had one in two weeks, where they had been happening every few days. Interestingly, the times it happened were always when the drive was idle.
So yesterday I backed up the Drobo to another external drive. Pulled all 5 drives and installed 4 brand new WD Red Plus 4TB drives. Went through the factory reset and set everything up - worked great. Then I started the process to copy the data back. When I checked on it after several hours I found the copy had stopped and there was the dreaded ‘disk not properly ejected’ message. I went through the event log and sure enough the Drobo took an ‘internal error’ and restarted. I did capture the diagnostics. Rebooted everything and started the copy again for the data that was the first time. Got up this morning and checked and it had happened again several hours into the copy. Restarted everything and started the copy (a smaller portion).
Each time when I see the disk not properly ejected message, the Drobo has restarted and appears completely normal - all lights green; data is accessible; going through the status screen everything looks good. Neither the drives nor the case are hot (barely warm) to the touch. I’ve tried to go through the logs looking for any telltale sign, but I can’t figure it out?
Really need some help!

Also, I am on the latest firmware 4.2.1 and the Dashboard is at 3.6.1…