I can recreate the problem on another pc which doesn't have a touchscreen, so I don't think that's the problem. I've tested it on 2 Windows 10 pc's and 1 Windows 7 Embedded and they all show the same behaviour. In my test application a second form is shown after you click on the edit and while this form is running code the text disappears from the edit.
I just noticed that if you close the second form, the edit starts to paint normally again, maybe this is why you don't see the problem? Instead of closing it, just minimize the form and click on the edit again, you should see the text in the edit disappear.