Hi All!

The passenger front seat on my 3D has a jammed fore-aft sliding mechanism. It won't slide forward when pulling on the adjuster in front, nor will it slide when the seat is leaned forward for people to get into the back. It's all the way back which makes my kids argue (every time!) about who has to sit behind it on the way to school.

I've had a peek under there to see if there was some obvious blockage, but the only thing I learned is that it's a complicated gizmo, quite unlike my Cinq!

Is this a semi-common problem? Any suggestions like perhaps trying to force it? This is an exceedingly rare car in Norway so finding any parts at a breaker is not an option.

Yes, i've seen this problem before twice.
You need to get the seat out, it's hold in place by 4 allen bolts. Then you have to check which one of the sliders it is blocked and moves badly.
Remove it(check the holes and you'll se the bolts) and check inside the track. You should see some obvious marks of metal friction.
Then bend that track inside to get clearance for the track itself to move smoothly.

At least that was the problem in our situations.

By some miracle it's not raining, so I just gave it go the pull the seat out. 3 of the bolts came out no problem, but the rear outboard one is hidden below the seat. I was hoping the outbound rail didn't participate in the whole catch deal so I'd be able to slide the seat forward along with the presumed stuck inboard rail, but so such luck.

I can't see where the outboard rail catch happens. Do you recall if it is more toward the front or rear?

Update: Mission accomplished! Thanks for the tips. After discovering some new yoga position, I was able to push the outboard rail release from the rear and get the seat to slide forward enough to get at the last bolt to be able to remove the seat. After cleaning about 3 lbs of gravel from the track, I saw that the lever had popped off the stub it was apparently supposed to be on. I guess some gravel had blocked the mechanism, and somebody pulled the lever enough to make it pop off the stud. Sorted!