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I have the same issue on parents 59 plate 6r 1.4 86ps SE ongoing for the last 6 years and multiple new batteries.
Wife’s SEL with a higher BCM is not affected and can start without issue after 2 months none use, whilst the parents Polo will randomly flatten its battery over 3 days (other times it will be fine after 1 week of none use???).

VW dealer want £179 just to “diagnose” and another 1 hour labour (£150) to do the software update.
They can’t even say if there is a software update available for these BCM’s until they diagnose, but I can say that the 085 BCM is on sw0025 according to VCDS.
Apparently they’ve never heard of this battery drain issue with the Polo.

Might just purchase a newer second hand BCM, hope that it has a newer software version and copy the coding across from the old BCM using VCDS.

That's what I would do, swap it for a newer BCM.

Freebster wrote: Tue Oct 11, 2022 10:11 pm I have the same issue on parents 59 plate 6r 1.4 86ps SE ongoing for the last 6 years and multiple new batteries.
Wife’s SEL with a higher BCM is not affected and can start without issue after 2 months none use, whilst the parents Polo will randomly flatten its battery over 3 days (other times it will be fine after 1 week of none use???).

VW dealer want £179 just to “diagnose” and another 1 hour labour (£150) to do the software update.
They can’t even say if there is a software update available for these BCM’s until they diagnose, but I can say that the 085 BCM is on sw0025 according to VCDS.
Apparently they’ve never heard of this battery drain issue with the Polo.

Might just purchase a newer second hand BCM, hope that it has a newer software version and copy the coding across from the old BCM using VCDS.

That car is right in the production period where this BCM programming was an issue, might be cheaper to find a VW dealership that understands that this unusual problem did and still with some cars still exist, they would charge for fulling a diagnostic check, then if they are willing to believe that this is a very old, but known fault, they can get VW mothership to let them know where to locate the patch and apply it, that extra task should only cost 0.5 hour tech time after the initial fully diagnostic check, the actual S/W update is always free.

Edit:- because this issue is now so far back in time, some dealership staff will not have come across it in all their time working within VW Group, it is a crap situation to be in, believe me, it is the "will it or will it not start" that is annoying!!

Maybe locate a useful VW Group Indie, they should be able to chat to VW mothership as they will have paid for the privilege.