I know you only wanted to hear from Seismic owners but the stackable are installed the same across the board. There is a mounting kit that screws to the floor and the washer is solidly fixed to the brackets. Just by your question some lazy bafoon might have not propperly installed your washer dryer. I have seen that a few times. You should also have a dryer vent hose running to the vent on the outside wall. Time to have th3 installer make good on their installation.
Neil & Karol 2015 Seneca HJ
Dolly tow 2017 Cadillac XT5, Toads 2008 Chevy 1 ton DRW, 79 Jeep CJ5