Do not load your existing 10-year-old save file. Create a new, empty test city. If it runs for 30 minutes without crashing, slowly add your buildings.
Note: This is for advanced modders. Nexl is a framework that allows modders to create interactive buildings. For example, you can place a specific factory that requires a specific resource input to function, or a cities xl platinum mods
For players who want a challenge, the vanilla economy can be a bit too forgiving. Do not load your existing 10-year-old save file
This is widely considered the most critical mod. It expands the standard game menus, allowing them to support the vast number of custom buildings and assets added by other mods without crashing. cities xl platinum mods