In the past week or so, I've been having multiple issues with Thunderbird. First, Thunderbird [v140] suddenly started crashing a few minutes after opening. I checked the help community and KB to try to find a solution and none of the following helped: Opened Safe Mode, the application continued to crash. Created a New Profile, the application continued to crash. Close Thunderbird, then deleted the Parent Lock File, the application continued to crash. Upgraded to v144.0.1, the application continued to crash. Uninstall Thunderbird, then reinstalled, the application stopped crashing. Upon restoring my profile from backup, I discovered several folders were missing. When I checked the Mail folder, I found many of the .msf files were missing but the folder file names were there. So, deleted my profile, created another, and restored from backup again only have the same results. This time I copied the missing .msf files from my backed up profile Mail folder, with the same results. I checked the help community and KB again and found a suggestion to copy the folder files and missing .msf files to the Local Folders folder. After copying the folder files and missing .msf files to the Local Folders folder, the missing folders appeared, including subfolders, but under Local Folders, not in my main account folder. I checked further and saw that all my emails were in fact in those folders, including in the subfolders. So I then closed and reopened the application and clicked to 'get messages' and discovered the message filters weren't working for the previously missing folders that were copied to the Local Folders. I thought OK, I'll just redo those filters. Later on, I opened Thunderbird to get messages and discovered none of filters for the previously missing folders that were copied to the Local Folders were working. I checked further and found that the folders were there, including the subfolders and emails except... the subfolders under the newest, most recent folder I created before the crashes started. Here's the kicker... after copying the subfolders' file under the newest, most recent folder and the .msf files back to the Local Folders folder and reopening the application, everything's there again. But after closing and reopening they're, gone again. After all these years of deleting and creating profiles and restoring from backups with very little or no problems, I've never encountered anything like this. I need a little help. Thanks.