Why doesn't online radio work through VPN L2TP, but does it work through VPN PPTP?

Question

VPN

There is no sound in the online radio when connected via VPN L2TP, but via VPN PPTP works fine.
And even when listening to the sites of radio stations themselves.
What is the matter and how to solve this problem?
Adding at 11:58 :
In my opinion - it has something to do with encoding the audio signal into a digital stream.
I add the initial data to the question - some radio stations normally listen through the VPN.
For example: "Echo of Moscow".
There is no sound from other Russian radio stations through the VPN.

Answer 1

Try reducing the MTU on the router and/or network interface.