我一直在做更多的工作，包括在另一个有Visual Studio 2017的系统上进行测试。
I have been doing more work on this, including testing on another system which has Visual Studio 2017 on it.
Both machines showed the same bug.
But with further work the problem seems to be involved with using the breakpoint in a datetimepicker event called when the date is changed. Putting the breakpoint in other places it seems to work normally.
So maybe that is where the bug in Visual Studio debugger lies?
Any Microsoft design engineers reading this?
It would be nice to see the bug fixed in the future.