Text-Edit and other apps lose ability to drag selection

After maybe 3 days of being open Text-Edit suddenly loses its drag-and-drop capability. Does anyone know why it happens and how to fix it? The hold-down-pointer simply can't drag the selection.

To restore normal draggability I have to close my documents and restart the app.

It also happens on an SQL editor app I use. These are the only two apps I leave open long enough for it to happen.

This has been going on for several years and through several OS upgrades. Trashing the Text-Edit preferences doesn't fix it.

It must be a bug in the OS because it happens in other apps.