MK cart does seat well

I purchased a set of empty carts and a big bottle of piezoflush to resurrect my 3800. I sealed it in a bag 3 years ago and took it out last week. Amazingly all channels print a perfect nozzle check except yellow.
I bought this:

I successfully installed the OEM chip from the original carts into the new empty carts and filled them with piezo flush. The MK cart tho doesnt go into the printer easily. If I push a bit I can get it to go in. But the printer does not see it. When I try to remove the cart it is stuck. The edge of the pcb of the little chip that is supposed to sit on top of the oem chip juts a little high. Here are some pix where I compare the defective MK chip to the normal LK chip

Not that it really matters because i never used the MK line in this printer. However, despite following the videos (soak head on piezoflush dampened towel 2 hours, clean head by running it over clean towel with piezoflush, 3 power cleanings and 3 regular cleanings- I still cannot get any yellow channel to work.

From what I’ve read it sounds like a clogged damper screen . Is there anything else I should do before taking this printer apart?