Well, yes: en is an integer derived from a string. But that does not explain the bug.
That's a bug! It was introduced in V0.19.
No that is not correct. At least not for Windows.
Press F1 (or select Help > Help from the menu) and a dialog will inform you were FreeCAD expects to find those files.
A classic problem is to have too many Draft_Snaps active. Especially the Draft_Snap_Near should not be permanently active.