should help you out Try deleting the solution user options file (.suo) where the debug/breakpoint information is stored. You will lose all solution user settings, such as breakpoint locations. When you have "funny" debugging incidents, this is the first thing to try because this file can get corrupted. If this does not solve the problem, then you have something else going on, such as threading issues, excessive memory fragmentation, garbage collection issues, dispose/finalize issues, and so on.
Threading problem with Visual Studio Debugger
By : user1384782
Date : March 29 2020, 07:55 AM
it fixes the issue In .NET you are not allowed to access a control from a thread that didn't create the control. In your code it looks like a separate thread is creating the splash form and the main thread tries to close the splash form. I suggest you do the other way round: create the splash form in the main thread and have the separate thread just update it.
Visual Studio 2010 Debugger problem - unregistered Error?