Had the 'low key battery' sign. Changed battery (Duracell) but key now dead and not working. Rechecked fitted ok and changed along side second key which is working ok.
Searched site but can't see this problem on a Mk 8 (2019)
I had a similar issue with the MK7 key (which is largely similar). Had low battery warning, put in a brand new battery and the next day low battery warning again. Happened multiple times until I put in a Panasonic brand battery. Not sure why that would make a difference but it was still working after a year