Hi vacrtino
Welcome to the Apple Community:
Re: AirPods Max louder on one side:
Wondering which device you use, and which app, when the issue appears.
Could it be the settings on iPhone / iPad / Mac / PC need adjusting
Eg: Adjust the mono audio, balance, and phone noise cancellation settings on iPhone - Apple Support
or
Change Sound settings on Mac – Apple Support
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Apple support have articles online that may, or may not, help troubleshoot:
Eg:
Learn what to do: If your left or right AirPod isn't working - Apple Support
How to reset your AirPods Max - Apple Support
How to clean your AirPods, AirPods Pro, AirPods Max, and EarPods - Apple Support
Connect and use your AirPods Max - Apple Support
AirPods Pro and AirPods Max Active Noise Cancellation and Transparency mode - Apple Support
If you use the AirPods Max with iPhone or iPod:
Customize headphone audio levels on your iPhone or iPad - Apple Support
If you use the AirPods Max with Mac:
Set up AirPods Max with your Mac and other Bluetooth devices - Apple Support
More Support if needed:
AirPods Support Website:
Find all the topics, resources, and contact options you need for your AirPods....
AirPods Support - Official Apple Support
All the best :-)