Hi Julian, the main things that are different between regular and private windows are:

(1) Separate cookie jars

Any login info and settings saved in cookies in the regular window are not available in the private window. This could be relevant if you notice that signing into your account in the private windows brings the problem over there.

(2) Separate web content caches

Private windows do not use previously cached files. To force a clean cache in the regular window, reload the page with Shift+Ctrl+R, or Shift+click the Reload button on the toolbar.

(3) Possibly different extensions running

Extensions need an extra permission to run in private windows, so in a private window, one or more of your extensions might not be running. You can see which ones are not running by going to the Add-ons page (Ctrl+Shift+A) and looking at which ones in the Enabled section do not have the purple mask circle icon.

Thank you jscher2000 for this complete answer. It has worked using the command "Shift+Ctrl+R" Very helpful, i appreciate it :)