Odd Tekkit lite lag

[Typhus]

So my friend owns a few server racks and he hosts a load of things like a webpage, teamspeak, and a minecraft server, (he had fiber installed so internet bandwidth is not an issue. well he had hosted tekkit classic for a long time and we decided to switch to tekkit lite. Only issue is now i get odd lag, my sound when placing a block is 1-2secs late, mobs are laggy when moving and attacking you, also blocks when i destroy them ever like 3-4th consecutively destroyed block will reappeared then disappear but if i moved to the space the block once filled in shoved me out of the way then disappeared, But let throw this entire experience for a loop and tell you that when i move around there is no lag, there is zero fps issues and the sound of my footsteps matches evenly and is not late. also when i hit a block to destroy it its perfect timing so its not lagged out, so what im trying to say is why are these handfuls of things laggy and frustrate me when i play but the rest of everything runs fine with no lag..... if anyone has a solution to this so i can fix the server files (by the way i know its the server b.c the lag is not there on other servers)