58.252.252.211 > 203.186.148.42

58.252.252.211 use pppoe. RouterOS ver 3.20.
203.186.148.42 use ethernet. Router OS ver 4.9.

I create the pptp server on 203.186.148.42 with 1464 MTU, 1464 MRU.
And create the pptp client on 58.252.252.211 with 1456 MTU, 1456 MRU.

There is no packet loss without the PPTP, and have 10%-15% packet loss with PPTP.
I have tried different configuration like MTU MRU PAP CHAP encryption etc... Also try L2TP but nothing change.

Can you help me ? Thank you !