Thanks for your replies guys, I'll be sure to let you know what the problem is when I find out!

Good Luck!

Just to confirm, your -winter wheels- are OE (not oem) and which version/ model number.
I realize that this has not recurred yet, but non OE wheels have a habit of causing this, i.e., rebalance more often, so thought I'd ask. (does not typically happen with recognized name wheel mfg., though there are stories even then, and the e53 wheel offset has been called important/critical since it can magnify issues).