Third row D.S. seat belt locking (booster seat use)

We have the same issue lately. I need to get it looked at next time I have it in. We don’t use the third row often but the few times we have recently, the seatbelt randomly locked up during driving (I wasn’t braking) and we couldn’t unlock it unless you unbuckled and put the belt back to it’s starting position, then buckled it again. Then it was fine for remainder of the drive. Happened with my daughter’s booster and when just an adult was in back.

Subaru has a lifetime warranty on seatbelts (functionality issues - not cosmetic), so even out of bumper-to-bumper they should cover it.

In general if you pull the seatbelt out rapidly it will lock, even if you're not braking. The purpose is for locking car seats in place, so it's by design not a defect. Try pulling the seatbelt out more slowly when strapping into the booster and hopefully you will not have any more issues.

Our 23 did that when we buckled a dog into a harness in the back seat. I had to let the belt fully retract and then it releases. It seems to happen when I maximally extend the belt - although occasionally it did it before i reached full length.