What can I do?!

Hello OCLP'ers,

Hope someone can help me out: at the moment I'm completely lost ;-(

I,m working for years now on my old faithfull MP 5.1 with all the upgrades with Mojave; a year ago I took the dive with OCLP, but since then the troubles began; I managed to upgrade to Monterey and as always before wanted to make a backup on a empty SSD (I have 3 1TB ssd's in the trays and 1 3TB normal HD, I have 1 ssd blade on a PCI card and 2 2 TB ssd blades on another PCI card) resulting in a lot of copies from the same ssd's on my desktop.

Now my startup and working ssd (SSD EVO; see screenshot) is almost full, Though, it isn't realy; I can see it is used by other ssd's. I recently wiped the TrayBackup1TB and installed a fresh Monterey with OCLP on that (but I can see it's also occupied by other apps or whatever)

So yesterday, I took out the TrayBackup1TB ssd, to see what happens (thinking it's not possible/advisable to install 2 bootable Mojaves on 2 different ssd's)What happened is that the computer did not boot and came with a long verbose list, which said it is unbootable and tried different startup procedures; nothing worked, also recovery mode failed, all with the long verbose scripts.

So I took out the EVO ssd blade on the pci card and it started up with TrayBackup1TB Mojave, switched off and placed back the EVO ssd and booted again from that; works like before (saying my SSD is almost full)

So now my question is; where did I go wrong and what can be done to solve this?

Please forgive me my ignorance; English is not my native language and I'm not a computer wizzard ;-)

Thanks in advance, all answers are much appreciated!

Chris.