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That whole sentence does not fix the problem to the OP case at all, OP doesn't have anything to do with lag. There's litteraly zero case related to players can OP themselves by a lag,
I know that, I specifically said that it was very unlikely and that a permissions plugin SHOULD help fix everything
Is that even a thing? Only players who have OP or players who have access to your server files can OP another player.
Im pretty sure there has to be INSANE amounts of lag for that to ever happen, OR a hack client and server backdoor could allow people to potentially OP themselves. Though the second is really unlikely (I mean, everyone in 2B2T isn't OP). It could be something like there's too many people on the server at once, causing so much lag that the authorization system just gives up. If that's the case then make sure you have stuff like EssentialsX, clearlagg, and NoCheatPlus to get rid of lag and secure the server. AND ADD A PERMISSIONS PLUGIN ALREADY! Whitelist the server while your configuring it to make sure no one screws something up btw. It's MOST likely a permissions glitch.
First of all NEVER give everyone in your server OP, second since spawn protection isn't the case, make sure permissions and commands and configured correctly, I had this problem but fixed it by adjusting my permissions plugin and spawn protection. Oh and if you're using world guard make sure to configure that too. Make sure you turned on block breaking/placing in essentialsX config if you have that.
The problem is that you are using too many mods/plugins. I suggest only keeping mods/plugins that fit the type of server you're hosting. For example, I run a private whitelisted server but had luckperms which is a permissions plugin, but it caused a lot of lag. So I removed it because I didn't really need it (considering it's a private server with only about 2-3 people on at a time) and most and if not all of the lag was gone. I also suggest installing a lag clearing mod since from what I've tried, it fixes a lot of problems for the server. Also, is it a Forge server for mods? if it's not and is a spigot/bukkit server for plugins, then I would recommend Paper MC for the server software. PaperMC supports all spigot/bukkit plugins AND speeds up your server by a lot. Also, I should have added this before but ONLY KEEP THE PLUGINS THAT YOU REALLY NEED!!! I can see that you have a LOT of chunk/biome altering plugins/mods, chunk loading is what usually causes the most lag on a server besides plugins which take the #1 spot so I recommend getting rid of them to (hopefully) solve both of those issues. For example, my server uses Paper MC and ONLY the plugins I need: (well BowHP isn't exactly a necessary but you get my point here)[Blocked Image: https://i.gyazo.com/9646ad9bf4bb27312cce94a43a4f8eaf.png]
I'm pretty sure some people have asked this question already but I can't seem to find an answer with the search feature.
On their Github and official website, it says they now support 1.16.1, without EssentialsX, I can't really update my server to 1.16.1.
I know I still can and it won't a major difference, but there's a lot of commands that I use for my server that are only available with EssentialsX and it would really annoying without them, thanks! Aternos is still my go to server hosting service though! 
