So the PO told me that when he bought the car a couple years ago, the owner before him had put a pair of flat metal strip "spacers" in the front of the drivers seat to tilt it back more, which made no sense to me, until I took them out. The seat base tilt mechanism seems to cam up and down like it should, but the front of the seat will pop down with any weight put on it at all -- like just getting out of the car. Only thing I can figure is that something is bent out of place where the cushion is mounted at the rear? Anyone else ever have this issue? google turned up nothing. The crappy looking metal strips aren't going back in...not to mention the safety issues of not having the seat bolted down properly...

 

I've seen this done on Honda (Civic/City) from 2015 MY - 2020 to make the front seats feel more comfortable for tall people. In putting in the spacers and re-bolting down, the seat geometry eventually changes ever so slightly that you'll never be able to fix. Watch out for the ABS module on the seat - as this is pricey and only has a 8 or 10 year warranty if defective.

 

You may be right, it’s like the frame of the seat has shifted. Watching the cam mechanism work at the front of the seat, it’s like the lower cushion has shifted forward about an inch too far and the cam links now let it “cam over” if it’s more than half way up. Might just have to pull it out and take it apart.

 

There's a bunch of people on the Honda forums and the "washer" spacers to tilt the front portion of the seat back at all settings was a popular, low cost farkle.