Hey!
Sorry to revive this very old message but i have the exact same problem!
Playback sometimes crashes either on the start or after some seconds of playing. I thought it was current drain issue at first, as if my USB port was not enough but even pluged on 2.1Amps wall outlet i have the issue.
It's really as if the DFPlayer reboots. The volume is reset to default after that crash.
Xenon board is OK, i'm controlling it via bluetooth and connexion isn't lost.
Im' powering theDFPlayer with the VUSB pin of the Xenon board.
Have you solved that issue since then ?
It drives me crazy !
Also @FiDel you mentionned this :
I found out that the speaker terminals are not “decoupled”: DC current is flowing through the speaker! This sounds poor and is dangerous…
Put an electrolytic capacitor in line with your speaker(s): Bigger = better… (220 - 2.200 uF/10V)
Attention to the correct polarity! (SPK1 = +)
Do you think this could be related to that ? May i ask more details about this ? Can I put it on any pin of the speaker ?
Also, i have an issue with the init command, but i made a specific topic for this if you have time to read it 
Thanks a lot for that helpful topic !