Hey everyone, here is the NWZ-A86x service manual. You should be able to enter the service menu to remove any volume caps but at your own risk. Although there is no guarantee that the cap will be removed. The key combination seems to be different from the original set back from 2012. Thanks to Robert for bringing this to my attention.
I have tried this on my E570 but it does not seem to enter the service menu, so if anyone gets it to work, please leave a comment here. More instructions what to do once you enter the service menu after the break.
Link to file