I have in the past and now that you mentioned it I do recall some blue screens which was part of the reason i removed the OC . Unfortunately i'm not sure when the issue (slowness) began because i hadn't tested in a long time. I will say the system has since been wiped an reloaded so if there was any corruption on the drive it should have been wiped out - unless the drive itself became damaged, which i doubt. According to the SMART data everything is fine.
So I do have some developments though... After testing on W10 1809 i reran TRIM multiple times (in 1809 with out a noticeable difference). I then switch back to the NVME (inland) W10 2004 a day later and ran Crystal disk mark. Surprisingly i got a 3,000MB/s sequential write, I ran a few more times and got the following on sequential writes. 3,000MB, 2400MB, 1080MB, 1080MB, 1080MB. I tried again today and got 3k, 3k, 2.4k 2.4k,2.4k (in MB). I did a 26GB file copy and then ran CDM again and got a 1080MB sequential write. My suspicion was the cache was quickly being exhausted and the speeds dropped.
oh, one other thing I did was to disable power save on the drive and changed the scheduler to run TRIM every day. So i'm feeling like things are looking up, speculating that If i run it again (about 10 mins later) the cache will have cleared up a bit a speed will have increased... So I do and and then i get this...
I'm ready to call it a day, but the OCD in me continues to test. 15 minutes later i'm up to 1020MB (seq write), another 10 minutes and i'm at 1435MB, 10 minutes later I get 3051MB/s. I'm speculating that the cache is slowly being zero'd out to eventually give me 1-2 good runs before degrading again. At least TRIM or the controller is finally cleaning out the cache now - even if it is a minuscule amount. (final run 5 mins later was back down to 2400MB).