I haven't heard of Max Altitude limits failing anyone else.I have not changed it. Is 30m the default setting? I did do a Firmware Update to both the drone and the SC tongiht. Would doing so reset it to a default setting?
The best thing to do would be to do some simple testing.
See if it flies higher than 30 metres.
If it does, the limit is not 30 metres.
Set the limit lower .. see if you can set it to 25 metres and test again.
Then try 40 metres and see how that goes.