PPTP >Disconnected

Hello
we have router os on vmware with valid ip, sometimes we get pptp error like this picture.
what is soultion?

[admin@mik] /ip firewall nat> print
Flags: X - disabled, I - invalid, D - dynamic 
 0   chain=srcnat action=netmap to-addresses=*Router valid ip* src-address=192.168.20.0/24



[admin@mik] /ip firewall filter> print
Flags: X - disabled, I - invalid, D - dynamic 
 0   ;;; allow established connections
     chain=forward action=accept connection-state=established 

 1   ;;; allow related connections
     chain=forward action=accept connection-state=related 

 2 X ;;; Drop Blaster Worm
     chain=virus action=drop protocol=tcp dst-port=445 

 3 X ;;; drop invalid connections
     chain=forward action=drop connection-state=invalid 

 4 X ;;; Spam Port
     chain=virus action=drop protocol=tcp dst-port=25 

 5 X ;;; Drop Blaster Worm
     chain=virus action=drop protocol=tcp dst-port=135-139 

 6 X ;;; Drop Messenger Worm
     chain=virus action=drop protocol=udp dst-port=135-139 

 7 X ;;; Drop Blaster Worm
     chain=virus action=drop protocol=udp dst-port=445 

 8 X ;;; ________
     chain=virus action=drop protocol=tcp dst-port=593 

 9 X ;;; ________
     chain=virus action=drop protocol=tcp dst-port=1024-1030 

10 X ;;; Drop MyDoom
     chain=virus action=drop protocol=tcp dst-port=1080 

11 X ;;; ________
-- [Q quit|D dump|down]

Capture.PNG