If Blockus is installed, upon loading the world, one will immediately receive the "connection lost message", even offline.
I am uploading my log for debugging purposes.

Blockus vs MBM.txt

I updated MBM to 0.1.8 bata, check if this is still giving you issues?

Looking though the log. I see full_slabs not loading generated models, sandwichable is missing textures, consistency_plus cant parse recipes, ect. Only place that shows moreblocksmod is at the loaded mods. There is a lot of mods installed, how did you determine that MBM is causing this? Could you elaborate the issue?

Sure, I know that logs don't necessarily indicate that the culprit is MBM but it was the last mod I installed and taking it out always fixes the issue. I have removed all my mods but kept MBM, then I started adding my mods in small batches. I had a suspicion that it has to be one of the mods that add building blocks, so I kept those mods (Nookbuild, Minegate, Blockus, Consistency plus) to the last place. I managed to add all my mods (with the exception of Blockus) and the game loaded just fine. With the addition of Blockus, this problem started surfacing again. If you need me to provide any other info, please let me know. But it is very probable that Blockus and MBM are both changing the same thing, thus causing a conflict. Otherwise, I really don't see any reason why a mod that just adds blocks would cause the game to crash in this manner.
Alternatively, you can also try running both of those mods together and see if there is a problem.

Here is a screenshot of both mods loaded. It maybe caused by a different mod combination? Can you send a zip file of your mods?

Thanks a lot, if that is the case then it has to be another mod addition of which make both Blockus and MBM incompatible. Just curious though, if MBM just adds blocks, then is it fair to say that it is probably another block-adding mod? Maybe Consistency plus or Minegate?
I have uploaded my mods as a zip file. I have 148 mods in total with APIs and other stuff included. If you manage to figure out what causes this, please let me know. Unfortunately, I don't have the technical know-how to do it myself excepting random trial and error, but I am given to understand there are some modder tools to help with that?
In any case, here's the link: https://www.mediafire.com/file/dfjeib3xm0byzxs/mods.zip/file
Let me know how it goes :)