I am unable to drag and drop messages from Inbox into a number of subfolders in a created folder. Other subfolders in this folder do not have this problem. When I attempt the drag and drop, a circle with slash image appears. When I attempt to move messages to these problem subfolders using 'right click' and 'move to', the problem subfolders do not appear in the drop down list. Same happens if I use 'message' and 'move to'. Probably related to this, the font of the problem subfolders recently changed to italic. I can access the existing messages in the problem subfolders. I have tried 'repair' on these subfolders, with no change. I am using Windows 11, Thunderbird 115.9.0.