Not sure if this will help you but I was experiencing this issue (no mods) after the most recent update and Lord knows EA will ever fix it so I found a minor solution.
Disclaimer: I only tested in Granite Falls since this was where I ran into the issue so I’m not sure if it will help in other worlds while on vacation.
To fix: make sure you have a ‘National Park’ or potentially any other NON- rental lot types in the world you are vacationing in. You cannot host social events while on vacation at rental lot types (I’m sure this is a glitch as it used to allow before the most recent update).
Hope this helps!
