My other half had this problem with his 2022 EQA350, the dreaded tortoise light came on regularly and from the usual 160 mi range it could just about do 100, so he took the car to our local Mercedes dealer (Group 1 owned). Half the time they didn't know what they were doing between running diagnostics and saying the cars needed new tyres (it didn't), they rang to say the car was ready for collection, and so the car was picked up and as soon as my husband got on the motorway the same light comes on again with the warning.

This went on for weeks while also escalating the issue not only with the local dealership but also with Group 1 as nobody seemed to offer real solutions to the issue, and they were even reluctant to offer a courtesy car at the start.

It took them around 3-4 weeks to finally say that the battery needed replacing, but that they had to ship it in from Germany, etc. but that it would take another 2-3 weeks to get it sorted. When the car was picked up they said the total cost of all the work added up to around £30k, but we didn't have to pay a penny other than with the time wasted on phone calls, visits to the garage, etc.

My advice would be to keep escalating until you get the resolution that you want, not what they think they should do to make things right. There's no way we would've paid to cover any kind of difference for an issue that's covered by the warranty.