27 inch 2020 glitching / slow

[Gareth1972]

Just got this start of the year and not worked properly at any point. I have multiple calls with Apple and they insist it is ok and not a hardware issue, have tried both Catalina and Big Sur plus wipe and reinstall plus everything else they suggested, it went into shop and then ran diagnostics and said there is no problem?!. . Finder jumps with even a few images and photoshop starts glitching after any kind of work flow builds up. Am currently dealing with Adobe who have run multiple tests (see below) also and they saying it the computer no the software. Anyone any ideas what I should do? I

 

[wilberforce]

Your RAM should not be at 2133MHz. It should be 2667MHz.
Post a screenshot of System Report, Memory.
Take out two sticks and leave in two matching sticks in Slots 2 and 4.
If still not OK, try the other two sticks in slots 2 and 4.
Also try your original Apple RAM in slots 2 and 4 (Even if this is only 8GB).

Not sure this is the source of the problem, but need to eliminate RAM as the issue

For Photoshop, try disabling use graphics processor (in Preferences, Performance). Not that this is a solution, but just to narrow down the source of the problem.