" Snaked it, unclogged it with 70 foot snake. "

Did you determine what exactly the clog was? How did you know the clogged was removed? Where does the line go? Tree roots maybe and your only getting it partially unclogged?

A snake can punch through a soft clog, yielding temporary results, but not clear the problem. A powered snake, run back and forth through the clog along with plenty of water to flush the debris downstream, is frequently needed.

JM$.02W

Most drain cleaners can run a camera down the line after they clear the clog. That will give you answers.

Yeah a clogged vent can do that. Air has to get in for the water to flow right, so if it’s blocked the drains back up even after you snake them. With only two people it’s probably not volume, more likely roots or a low spot in the line holding gunk. Camera inspection is usually the next step so you can actually see what’s going on.

Do you flush "flushable" bum wipes? If you are using them and flushing them, start putting them in the trash instead. I had constant problems in a rental house. I eventually figured out the "flushable" diaper wipes were part of the problem. The other part, I guesses, was a tree root in the pipe, that the wipes got stuck on, but that was too far into my yard. That house had very old clay pipes. Any leakage was minor enough if it did anything, it made my garden flourish. Although, maybe there was no root in the pipe. Who knows? Certainly, the problem went away when I started putting the wipes in the trash.