Console bug?

I dont know how I can explain this but, everytime I launch my server and I'm looking at the console, it gets a huge spam of "Object successfully summoned" by a repeat command block? I cant find the repeat command block, and when I set /gamerule commandBlockOutput to true, it doesnt appear on the minecraft chat. It only appears in the server console and server logs.. I dont know if this affects the server performance, but sometimes I would only launch the server for configuring plugins but I cant see anything because of the Command Block that is summoning those objects..? And everytime we do /kill @e[type=!Player], it doesnt seem like its really doing anything because it just kills all the entites (except us of course) and it doesnt include a large number of mobs of the same kind..

I hope someone knows the answer to this because its so annoying

The server version is Bukkit 1.12.2 and I am using Optifine 1.12.2
My friends claim that they didnt put any command blocks and removed it all.
Is there a way to remove the command blocks using the console or any plugins?

I think I'll use MCEdit once I'm back home. And yeah I am an op in my server. Thanks for replying anyways!

Found the solution!

I used MCEdit to remove all the command blocks in the main world and deleted The End and Nether worlds because we dont really use them lol. But one of my friends claimed that there was a repeat command block in the end that summoned the "objects". However, he told me he is going there to remove the block but before he removed it the spam already stopped? Was it a command block glitch? Anyways, we deleted both The End and the Nether and the command blocks! Thanks for your help so much!