Glc 220d 2021

Had the car 3 years now. Few days ago. Baffling noise coming from behind the glove box. Sounds like the ventilation thing is getting blocked intermittently, but I played around with fan and turned it off and it made no difference. Car has been plagued with issues. The camera for multi beam led is dirty and Mercedes refused to fix it under warranty even though when I spoke to Mercedes from overhead panel they said it’s a sealed non maintenance component. Left window sometimes goes down when I press up. Then after few attempts it finally goes up. But this noise I can’t work out what it could be. Any ideas from Merc techs would be very useful. It’s like putting your hand and covering the vacuum cleaner pipe. That suction noise changing it’s a bit like that. Opening the engine bay it’s coming from further inside behind where the windscreen washer fluid tank in.
Any tips what it could be and if it can be fixed simply by ourselves or Mercedes specialist. Few weeks back aircon stopped working so took to Halfords to regas, kid thought machine wasn’t working so didn’t charge. Went to specialist. It was the aircon sensor that had gone but to change it they had to empty the gas and refill it. All in £200. Not too bad.