WD SSD 1Tb SATA Low speed with old files

Almost impossible to work with old files as they opening and copying very slow. It’s interesting, that the tests (for ex, Crystal Mark) show perfect speed, but dashboard demonstrate the real situation (the speed of folder copying on the attached image - about 2Mbs.) The newer the folder or file - the higher speed of working.

I tried various cables and the software version is the last.

Seems to be an issue starting to show now on several different drives. I was able to resolve for my device using mydefrag to force read and rewrite of files. This uses up drive endurance but that’s better than a drive too slow to use.

Thank you for advice, I’ll try! Now I’ve just decided to copy all files to another drives, probably format, and copy them back. It says that it takes several days for 500gb - so annoying!