Of course, this being a snapshot, I'm not surprised this error is popping up. It's not even an error message, it's just a weird glitch or bug that prevents me from doing cheat/OP commands as an administrator on my own server. I'm even OP on it. 

So, the issue is that every time I set up a custom command with /trigger functions (like /trigger spawn) I suddenly start getting problems with admin commands. I use command blocks for these trigger commands. I used this specific tutorial as well:

https://www.youtube.com/watch?v=FzTvN7yYft4

It worked so far until I used an admin command. The server crashed and admin commands are wonky, and have to be spammed for a little bit before working. After the first try an error that says "An unexpected error occurred trying to execute that command" comes up. I restart the server and admin commands work (85% of the time anyway) except for /op. It works if you do it twice, but it always starts with "An unexpected error occurred trying to execute that command." This also appears in the console when I type out these commands.

Now, the admin commands aren't the only issue. Another issue is that command blocks can't be opened. I turned down spawn-protection to 0, I set enable-command-blocks to true, and made sure I was OP and in creative mode. Still, nothing works. I tried to let my admin work it out, but even they can't do it. 

I made sure to test if the datapacks I installed were the problem but they aren't. I downloaded anti creeper grief, anti ghast grief, kill empty boats, more mob heads, multiplayer sleep, player graves, set home, and custom villager shops.

Datapack site: https://vanillatweaks.net/picker/datapacks/ The datapacks work, and don't show any sign of being the cause. It's the trigger commands. Idk why creating a trigger nearly destroys the server...

Hopefully this was enough info for this bug to be resolved...

I sadly have no sources to send this issue. (Right clicking the command block doesn't work either...)

If you need me to record proof of not being able to right click/open command block GUI prompts, let me know.