Both mine did. I reflowed and fixed them both. That said they were older. The thing is if they lose sync from low main battery they won't re-sync on their own so I'm thinking maybe an antenna receiving problem. (since if I'm reading you correctly they work on and off).

When mine (both) had bad solder joints they would usually work immediately after locking the car or after open/close the hatch as if at that time the car raises the gain on the receiving antenna.

I can't remember as It was five years ago but I think if I locked the car with the key blade I could unlock with the fob for a minute or so but if I went to the house and back five minutes later no go. Then I would unlock with the key blade and for a minute again I could lock/unlock with the fob as much as I wanted for the next minute or two.

Symptoms sound familiar? That's why I mentioned. From reading many dozens of threads of keyfob not behaving but sometimes working 5% battery 90% solder joints 5% something else.

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