In two of our ASP.Net Web Applications, in the Web.Config file, we've set the Custom Error redirect to our custom error page, and set the mode to "RemoteOnly" so that when we debug locally we see any unhandled exception message displayed on the "Yellow Screen of Death" - "YSoD".
This week, we discovered that when an unhandled exception is encountered, all of a sudden we're getting our custom error pages, instead of the exception details in the "YSoD".
This applies to only two, of the several applications we're running. I've searched high and low for a similar problem/solution, and haven't found much.
I'm trying to determine if this is an Application, IIS, or Visual Studio configuration problem. It just started happening, and there were no significant changes made to the server, etc., to potentially explain the problem. We have enabled IIS Failed Request Tracing, but I couldn't find anything associating this with our problem.
Given this information, what can cause this sudden change in behavior?
The back-end is a SQL Server database, using Windows Authentication, on an AWS VPC.