When I play on my friend's server, I experience severe lag : My friends don't see me move, I can't open chest, Chunks don't load, etc, Weirdly enough, this lag only occurs on this modpack, I have tried other modpacks such as unleach and FTB skyblock. I can play the game just fine on single player.
I have already tried to maximise my Pc performance (allowing 4 Gb of Ram for minecraft, changing the options to maximise the performance, etc), I checked my internet connection and it was fine and of course, I tried deleting and dowloading the modpack again, Nothing is working.
If anyone has any idea of what I should do, any help would be greatly appreciated.