1. Being the one who is gonna host, press ~ (below the Esc key) on your keyboard to open your console and type the following command:

net_bSubscribedItemsChecking=0

Here is a screenshot of what it looks like:

2. Now hit Enter and close the console.

3. Create your listen server as usual.

4. Make sure that the clients who are trying to connect to you have the same mods as you. You can also tell them to apply the above command to their game, just in case.

And there you go! People should be able to join your server with no errors, restart loops or anything like that.