PCIe M.2 unreliable mounting in Mac Pro 2019 via OWC Accelsior

Here is my story:

I have two OWC Accelsior 4M2 cards in my 2019 MP. One Accelsior is filled with 4 original OWC 2TB M.2 units (RAID0), and the other includes 4 2 TB Sabrent Rocket 2280 SSDs (RAID0). Presently running Sonoma. 

Cards were installed in 2021, and have never mounted reliably. I have tried the tips that have been mentioned in a corresponding thread on MacRumors, to no avail. I hoped that OWC Softraid would help, but it does not.

To only solution that works a bit is: using Apple's PCIe expansion slot utility to redistribute slot designations and rebooting the system. About 50% of the time, both Accelsior will then mount. Else, I have to try again.

Also, I observe that a first booting sequence of the MP appears to stall for about a minute when one or both of the PCIe Accelsior cards fail to mount. One would fear that the MP has a hardware bug regarding its PCIe slots.

In the past, I also included a Promise Pagasus J2i, including two 4 TB ssds. I have removed it to reduced system load, and I think it had the same mounting issues. It appears that having the additional J2I installed made matters worse. I will investigate this further now, hoping to make some contribution in finding answers.

In any case, I strongly hope that Apple (and OWC) can provide a solution to our problems. We paid for expensive machines (which are absolutely awesome) and these mounting issues are just annoying to say the least.