Hi, I know getting the F35 error can be frustrating. To keep the laundry going you can try unplugging machine for a few minutes. Eventually, it could get to where this does not work anymore and you will have to repair machine.
There is a site at F35Error.com
that has deeper troubleshooting process to help you determine if it is the analog pressure sensor, CCU or maybe your CCU just needs repaired with a kit since it has been determined that there is a common failure on the CCU that can be easily repaired.
I would suspect in your case that it is an issue the with analog pressure switch or CCU because the analog pressure switch reading maybe fooling the CCU into thinking the water is draining too slow if you have checked the water discharge path and found it to be clear.
I hope this helps.