[lo bux racer]

The seat rails aren't aligned right. There are two catches, what you are getting is one catching and the other waiting for the seat to flex so it will also lock. If you install the seat out of alignment, this happens. I learned this on my '88 GTS Corolla. Exact same symptoms.

The easy way to fix it is to loosen the mount bolts on ONE of the rails (front and back), then flex the seat until it locks both sides, then tighten the two loose seat bolts. Your problems will disappear.

 

[lo bux racer]

An easily fixed Toyota issue.

 

[lo bux racer]

I take my seats out to clean under them about once a year. I found this out the first time I put the seats back in my GTS Corolla way back in 1989. It pissed me off for a good week before I figured out what I'd done wrong and corrected it. Now I just do it out of habit when I install the seat.