sure that this is leak in the drain or the drain process.
THats what I am saying. Just maybe something crawled into that pipe or whatever and when the washer drains the pipe cant keep up with the flow of water. Just pull the washer out and run it. Could be an easy find. Now the FIX might be a challenge LOL, Sorry for all the headaches you going through right now.....
And when I worked at west beach resort on the island a bird tried to get into the vent pipe on top of the roof. Took forever to figure it out, but I did and just had to cut that section of pipe out and sure enough there was a drowned bird head first into the vent line, just below where the bathroom sink tied into the vent pipe.
And when I was taking care of those 248 apartments in TX, we had a commercial shop vas with 2 HUGE suction motors on top. It would pull a max vacuum and it would suck anything out of the drain pipes. I wont go into detail some of the crap I pulled out with that machine LOL
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