F21 and SD error codes

About 2 of 3 loads I have an SD error code. I have twice in the past 3 days had an F21 error code. I understand from the manual that SD is suds and F21 is a drain problem. I checked and I don’t have a clog in my drain pipe in the wall. The water is exiting the washer slowly and it seems to be taking a while for it to completely exit the washer. Any suggestions on what I should start with? If the pump were to be going bad, would there be any water at all coming from the drain hose? Is there possibly a clog in the hose and how do I check that?