As far as I am aware and I had same problem with my W211 E55 Display faulty indicates a problem with communication between various CAM in car. Mine turned out after some considerable time looking to be a corroded board in the boot. It threw up many weird errors including oil, battery and SBC etc.
I have had four teenagers who have gone through the learning to drive process in the last 8 years.
They have all varied in the number of lessons but probably quickest was about 20 (oldest son) and 40 (oldest girl)
As for driving school reviews from others is always the best way
Mine wore like this on the rear when I had the ride height set too low on my ELM
It was sometimes rubbing on the side of the wheel arch liners, which although only plastic were highly abrasive (like sand paper)
Draytek Vigor routers are very good have been using the for years these will offer the type of isolation that you require
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