Unable to Debug XNA Game1 Class - VS2015

As the title states, I am unable to debug my Game1 class only. If I place a breakpoint in Game1 and start debugging, I get the message

The breakpoint will not currently be hit. The source code is different from the original version.

I have not made any recent changes to this file. If I place a breakpoint in a different class, it works just fine.

I have:

Manually deleted the PDB files
Restarted Visual Studio
Cleaned and rebuilt the solution
Closed and reopened the solution
Restarted my computer

Despite not making any changes, the debugger thinks my code file has changed and won't hit any breakpoints. I can turn off the "require code to be the same" option, but I'd rather not do this.

Edit: It's also worth noting that this was working before. I've been working on this particular solution for about a month, and this just started this morning. No changes were made to the file after the last successful debug.

Does anyone know what might be causing this issue?

Solution

Make sure the problem project is being built as part of the current Build configuration. :-)