Sud/f35 error. Tried everything, now what?

We have the 5000 series front load washer and have the suds and f35 error. We have replaced the analog pressure switch. Not a fix. Replaced the drain pump because the propeller was making a bad noise. Not a fix. We have checked all hoses, the air trap, everything. Down to thinking it might be control board but hate to spend the money without knowing. Do the diagnostics and it won’t go past c00. We are very frustrated and we fix almost everything ourselves. Any other ideas?