Dear Madams and Sirs, i hope you can help me. As a (web ) developer (and fan of Firefox) I use Firefox every day and i restart the browser serveral times a day. I use a Dell U3417W as an external display (widescreen, notebook display is deactivated if i use the external display) under windows 10 & 11 and i want Firefox at the right half side of the Screen (using windows + right or manuel positioning/resizing of the Firefox window). At start of Firefox, first it will fit the right side of the screen without any offset (last saved position from xulstore.json) - only for a very short moment. Immediately after the start the window will automatically repositioned to an offset of appox. 5px from the right/button position (see attached screen). Then i have to use windows + right or mouse drag to the right border of the screen to get the right position again. At next start of Firefox the Firefox window is at the same offset position again. I searched the web for serveral ours to find a solution: I tried to Refresh Firefox, delete xulstore.json, i have only the standard dark theme active (FF 128.03 and earlier versions, now in win11, win10 the same), tried the fingerprint.. = false approach, nothing works. Firefox is the only application with this behavier. Chrome, Edge i.e. does not have the kind of shifting... Thanks in advance and greetings from Berlin Daniel