High packet lost on 6to4 tunnel

Hello and happy new year

I have a weird problem with 6to4 tunnel and i hope you help me to fix this

I have a CHR vps in France, there is a 6to4 tunnel between my home in Iran to France, problem is i have 50% packet lost on my 6to4 tunnel (tunnel ipv6 is “2002:808:801::2/126”) but not even 1% on vps static IP !!!, what is weird ?

my uncle have a 6to4 tunnel to my vps in France without any packet lost.

  • we have same ISP with same bandwidth and same route
  • we have mikrotik 951 updated to 7.6
  • same tunnel and setting
  • same vps
  • ping to vps static IP is without packet lost

i just want to say everything is same between us, but why i have 50% packet lost on my tunnel and he don’t ?

i tried downgrade, rebooting, removing and add the tunnel again…

no one knows anythink ?