I attached a file of a screw assembly.

I am adding this to another assembly.

After adding the screw, I right click on it in the design tree and click on disolve sub-assembly.

After this I get many mate errors.

When mating the screw assembly to the plate I use 1 concentric mate for body of screw and hole in plate.

I use 1 coincident multi-mate for plate and bottom of top washer.

I don't understand why I get mate errors.