favorites problem

[Sorcerer25]

hi, i have Trackmania free version
and i have 2 servers in my favorites

but i can't add any more of them, message is: "you need to remove some to add more"

afaik there supposed to be 10 favorites slots
and my guess is that servers which are not there any more but still present in my favorites (even that i can't see them), so they block me from adding more and i searched everywhere to erase off-line servers from my favorites, didn't find any way to do it

so the question is:

how do i delete off-line servers from my favorites ?