Connection problem client vs server

Ive tried to connect to the Dude server 10 times but only 1 attempt is successful. I dont know why.
Server is virtual machine ROS 6.49.17, client 6.49.17 from win10.
When I tried to connect via client I can see getting stuff, rx/tx traffic about 2sec and then nothing.
Log results.

12:27:42 system,info,account user admin logged out from 192.168.30.102 via winbox
12:27:42 system,info,account user admin logged in from 192.168.30.102 via winbox
12:28:05 system,info,account user admin logged out from 192.168.30.102 via winbox
12:28:11 system,error,critical login failure for user admin from 192.168.2.248 via winbox
12:28:21 system,info,account user admin logged in from 192.168.30.102 via winbox
12:28:25 system,error,critical login failure for user admin from 127.0.0.1 via winbox

2.248 is Dude server, 30.102 is my win machine via vpn.

I can`t see any logical reason why only every tenth attempt (on average) is successful.