A data point on ASR. No matter the brand, wheel speed sensors can age, become covered in metal dust changing their output, this can cause an ABS system to actuate when it does not need to . I'd expect this would have some effect on ASR as well.

Somewhere in the MB service manual there is a way to completely disable ASR for dyno testing, might be a good idea to try that. The snow chain button supposedly only mutes ASR not completely shutting it off. In the day someone was selling a high dollar magic box to shut off ASR but it just turned out to be a few relays that put ASR into dyno mode. Have a look on this site and others for info.