As I open an esisting events in TB Lighting Calendar, even a Google Calendar event or a CALdav one, TB delete the alarms previusly setted. If I open an event and close it TB ask for saving the modified event because TB deleted the alarms... Deactivated exstensions without benefits.

Extensions installed Auto Resize Image 1.0.0 Calendar Tweaks 7.0 CardBook 30.9 Display Quota 0.3.8 Folder Pane View Switcher 2.0.2 ImportExportTools 3.3.0 Lightning 6.2 Lightning Calendar Tabs 2.1 PrintingTools 1.3.0 Provider per Google Calendar 4.4.1 QuickFolders 4.10 StartupMaster 1.6.5 Theme Font & Size Changer for Thunderbird 64.1 ThunderPEC 1.9.1 Color Folders 1.1 false Duplicate Contact Manager 0.9.2 false Print Preview Button and Keyboard Shortcut 1.0.2.1-signed.1-signed false Year View 0.4.5 false