Imprecise BC? / Switch lighting

First of all a happy new year and always a good ride! Have a question about the BC….Have the impression that it works somewhat imprecisely with me. The clock feels something. I always put it on the news on the radio and have to put it occasionally, although I already introduce it… 🙂 The daily kilometer counter shows about 400m more than the mechanical daily counter at about 600km ride. The average speed is somehow always 55km/h….:-) Consumption, temperature Is everything not an issue, of course, would I be interested to see if you have seen something similar before?! The light of the switch for the rear window heating / heatable mirrors is defective. Unfortunately, in my well-assorted car accessories trade, there is no such thing…:-( If I go to a Volvo Glass Palace tomorrow, I will certainly pay a fortune or is that a cent article there? VG Bird