Auxiliary battery issue in my GLE – anyone dealt with this before?

I've got a 2019 Mercedes-Benz GLE that I absolutely love, but recently I've been dealing with a frustrating issue that I just can't seem to figure out. A few weeks ago, I started getting a warning message on the dash saying "Auxiliary battery malfunction" and ever since then, the start-stop system hasn't been working properly and I've noticed that the ECO mode doesn't engage like it used to. I did some research online and apparently the GLE has a small auxiliary battery that powers things like the start-stop system, the ECO mode, and some of the other electronic features, and when it starts failing, you get all sorts of weird issues even though the main battery is perfectly fine. The problem is, I called the dealership and they quoted me an absolutely eye-watering price to replace it – we're talking several hundred dirhams for what seems like a tiny battery that probably costs a fraction of that. I've been browsing around online and came across a website that seems to have information about auxiliary batteries and replacement services – I think it's something like dubaicarbattery dot ae slash auxiliary – but I'm not sure if they're a physical shop or just a resource page. Has anyone here actually used them or similar services for their auxiliary battery? I'm looking for a reliable workshop that can diagnose the issue properly without charging me a fortune. I've heard that some independent garages can do this for a much more reasonable price, but I'm not sure which ones actually know what they're doing with Mercedes vehicles and won't mess up the electronics. I'm also a bit confused about whether I actually need to replace the auxiliary battery or if it might just be a fuse or a connection issue – I've read online that sometimes it's just a blown fuse or a loose wire, but I don't really have the tools or expertise to check that myself. I'm based near the Marina but honestly I don't mind driving across Dubai if it means finding a trustworthy garage that won't overcharge me. If anyone here has had their auxiliary battery replaced on a Mercedes or similar European car and can recommend a workshop that does a good job at a reasonable price, I'd really appreciate it. Also, if anyone knows roughly what this service should cost, that would help me know if I'm being quoted a fair price. I'm hoping to get this sorted soon because the warning message is starting to annoy me and I'm worried it might affect other systems if I ignore it for too long. Any advice would be massively helpful visit here https://dubaicarbattery.ae/auxiliary.