Initially when carrier isn't working properly the lock mechanism is simply sticky. It won't break until you pull too hard while it's broken. You can take it out, clean the lock mechanism and put dry graphite lubrication on (doesn't get gummy when cold). If you can't open from inside door handle then likely the latch the problem cross fingers not that it's pricy.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)