It's weird I have to keep changing the speed for different maps speeds vary on smaller maps vs big ones
That's why we asked you about scripts.
Speed does NOT change on its own, it always has a command that changes that speed. That command can either be in the events or in the scripts, but you have to find that command to prevent this problem from happening again.
Add several of the sample maps for testing. do not place any special event on them, only a fe transfer events to get on them and to change between them (use the quick event option, do not make the transfer manually).
If the speed keeps changing while you are on those maps, then the problem is either in the common events or in scripting - check out all your common events and if you don't find anything there, then give us links to all scripts you've put into your game.
If the speed no longer changes on those maps, then there is something on your regular maps that triggers the speed changes - either directly or indirectly from the map events. Then check out every map event on one map where the speed changes happen, and erase all speed commands in them (including those you put there to correct the speed).
If the speed doesn't stay the same after all speed commands are erased from all events on those maps, then there is an indirect effect in function - usually this is when a script configuration is linked to a switch or a variable that has a secondary purpose in one of those map events. Again, give us links to all scripts you have in your game to check that.