I completed my first successful PokeRadar hunt at a chain of 40, and the chain ended right after I caught the shiny. Do PokeRadar chains always end after you catch the shiny, or did I just get unfortunately unlucky.
No.
The radar can continue after finding a shiny at 40 chains.
Here’s a video of someone finding multiple shinies in the same chain that goes to 50
Hope this helps!