Duplicate emails in folders + EM client super SLOW šŸŒ

Hi everyone,
Since weeks, I found a lot of duplicate emails in my foldersā€¦ It sucks and drives me crazy!
Also, it takes ages to open certain emails, move them or scrolling through. No itā€™s not due to my Mac, the last one, M3 chip and half full Go, it should work very smoothly, as it did when I installed Em Client a year agoā€¦
Can you HELP?