Server teleporting players back every few seconds (1.12.2)

While my friend and I play on my server, we would constantly get teleported back every 10 seconds or so. Commands work(slowly) but pressing tab doesn't autofill even though it works on my private world. It would take some time for the chest, crafting table, or furnace interface to show up and occasionally it would take blocks about 5 seconds to actually break after right clicking. It would also take around the same time after right clicking for mobs to be hit. We use the quark and quark oddities mod. Maybe that's the problem although it runs quite smoothly in my own worlds and we've played on a smoother server that includes more mods before.