Rider debugger not hitting breakpoints with Xamarin

I have recently switched from Visual Studio 2017 to Rider due to a host of weird issues using Xamarin with VS. Rider seems to be running a bit more smoothly with Xamarin but for one issue: the debugger often refuses to hit breakpoints. Half the time it will work just fine, and the other half the time my breakpoint is replaced with a Ø symbol, which shows the message "Not found associated module for breakpoint", as shown in the attached image.

I'm enjoying my experience with Rider so far apart from this highly irritating issue. I've read this kind of issue can arise from using separate drives but my solution file and Rider install are both on the same drive.

If anyone has found a solution / workaround for this I'd love to hear it!

Thanks,

Tom