Why does Frigidaire washer model FWS645GFS1 knock during spin?

SOURCE: Front load Frigidaire Gallery washer

You are having a door switch problem change it out and you will have a new washing machine.

SOURCE: Frigidaire front load washer won't drain or spin

This often is a drain hose that is too low or a drain hose that has been pushed too far down inside the stand pipe....the water is actually siphoning out of the washer. Do not "seal" the drain hose to the house plumbing pipe, this will also allow the water to be siphoned out.

SOURCE: My model #gltr1670aso makes loud noises during spin cycle

Usually this is due to either the drum support breaking or the back bearing being bad-neither easy to fix- or worth it. Try lifting the drum up and down, if it moves up and down they are bad. I see this a lot, and the price of repair isn't worth it. Craig

SOURCE: ATF6000ES front load washer won't spin during regular cycle.

clogged filter will cause this error code. I have the same washer and the filter located inside the rubber boot attached to the pump was full of junk. there was enough room for water to get thru but not enough for full volume. clean it out and it should work. note : its a pain to get the boot back on so be ready and take it slow. this worked for me.

SOURCE: Fridgidaire Washer has a loud knocking noise during spin cycle.

You need to replace your washer, the Inner tub Spider broke.. I repaired mine, With me doing the labour, $285 just for the part alone. plus about 3 to 4 hours labour.