It seems there is a battery drain issue due to a £300 electronic module on the bike. This causes excessive current drain when the bike is parked up. The module has been replaced with a different spec one in newer bikes but BMW do not seem to be doing a re-call despite many problems worldwide. My 2016 GSA has the same problem and I replaced the battery with a Yuasa one (Never ever had to replace one of these on any bike) and lo and behold same problem. My bike is out of warranty and BMW have a bit of a 'swallow my nob attitude' in such cases. I am going to try my local dealer and if they won't help - which I suspect they won't, I will be leaving this forum and BMW forever!