Selecting "Local Artboard" will change Artboard Size to A4 in Canvas Options dialog
- 
					
					
					
					
Before you go through the repro steps...
- Select the Canvas (Canvas 1) in the Canvas & Artboard panel
 - Bring up the Canvas Options dialog
 - Select the Artboard tab
 - Change the Artboard Size dropdown to Custom (if it's not already)
 - Uncheck the Local Artboard checkbox.
 - Close the Canvas Options dialog.
 
Now...
- In the Canvas & Artboard panel select the Canvas (Canvas 1).
 - Bring up the Canvas Options dialog
 - In the Canvas Options dialog select the Artboard tab.
 - Check the Local Artboards checkbox. The the Artboard Size dropdown will change from Custom to A4. The Artboard Size dropdown should stay on Custom since 500x500 is a custom size not A4.
 
Video:
https://www.youtube.com/watch?v=W3IkVnxLzFIVS 1.1.095
 - 
					
					
					
					
@pentool Replicated, will be fixed in the next build.