Hey Michelle, how are you doing?
First, I apologize for the errors you encountered. After analyzing the log you sent (and thanks for that!), it looks like a failure occurred during the map's `update()` call, seemingly involving a function from `VisuMZ_1_EventsMoveCore.js`. I added that plugin to my project and was able to reproduce the error; I then added the missing variables to my plugin's setup to satisfy `EventsMoveCore`'s movement update requirements, so I believe that is now resolved.
I also noticed an error regarding the creation of the Player 2 sprite on Player 1's screen, and vice versa. This happened because, when I originally designed this plugin a long time ago, I couldn't solve the dynamic update and movement issue without causing an FPS drop (hence the "Parallel Lives" concept—players weren't supposed to meet, lol). However, time has been on my side, and I now know how to fix that problem, so it is resolved as well.
I also added an update function for when you use parallax backgrounds on the same map; now, they update dynamically on both screens instead of just one. Previously, the parallax would load when the map started but stop updating, which caused a black screen.
I also improved the camera to allow characters to get closer to the map edges without leaving the view due to RPG Maker's built-in grid limits.
I included a small, working demo file to demonstrate interactions between the two players on the same screen; I hope it helps.
One note: DSX (Dual Screen X) is a bonus included in the package, but it modifies the exact same classes as Parallel Lives. They weren't designed to work together, so errors may occur if both are enabled simultaneously; personally, I don't recommend using them together.
Regarding your design, we’ll need to give some thought to the HUD issue, since Player 2 isn't treated as a second player (`gamePlayer()`) but rather as a movable event; significant, perhaps radical, changes might be required to make it behave the way you need.
Please download the V30 zip file again; it already includes all the fixes I mentioned here.