Ah yes, I have had this happen before. Make sure there is not kid debris in the floor where the seats lock. (happened to me) Make sure your third row floor mats are in properly, if they shift too close to the floor lock, it can prevent the seats from fully locking. Have you slid the second row back and forth and tried? I have had to stagger the seats and do it a couple of times.... If all else fails, it could be a sensor which could have been disconnected due to a busy bunch of kids in the back of the X. last but not least..... Hello dealer.

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2012 X5 50i ZAP(2VA, 336, 465), ZTP, ZPP, ZPS(6VC), ZCW, ZRC, 322, 4UB, 4NC, 610
2011 ///M3 Silverstone II
2011 X5 50i(lemon)
-- SOLD --
08 550 Msport
07 X5 4.8I sport
04 545i sport
02 4.4i sport
01 540I M/sport
00 SL500
97 SL500