Question NVME SSD on m.2_2 slot disappears/not detected after installing 2.5" SATA SSD

Jul 24, 2020
Mobo: MSI B450M Mortar Max (Bios updated to latest version before Beta version, works properly before so saw no need to update)
M.2_1 Slot: Adata XPG SX8200 Pro 512GB (OS drive)
M.2_2 Slot: Teamgroup MP33 1TB (worked perfectly before installation of 2.5" SATA SSD)
SATA SSD: Samsung 860 Evo 2TB

My problem: I installed sa 860 Evo (Drive E:) in the SATA Slot 3 and everything worked fine, so I transferred my game files from the MP33 (Drive D:) to the 860 Evo. After a while, as I was browsing other files on the MP33, I got errors in opening files. I tried refreshing File Explorer and the drive was still there. Checked Disk Management and it was also online.

So I restarted my PC and went to Bios and the MP33 was no longer detected (the SX8200 Pro and 860 was detected). When I boot to Windows, the drive is also not detected in Disk Management, File Explorer, and SSD Toolboxes.
I tried changing SATA ports and the problem still persists. If I remove the 860 Evo, the MP33 is automatically detected. Re-installing the MP33 is the only way that it is detected by the system again while the 860 Evo is also installed. Even then, it eventually 'disappears' once I boot into Windows (indicated by errors in opening files).

I've read the manual of my mobo and there shouldn't be a problem since the M.2_2 slot only disables the PCI_E4 and not any of the SATA ports. Or does this mean that I can't use SATA SSDs if I M2_2 slot is used?

I am at my wit's end. Any help would be appreciated.