Premiere Pro 2020 has been very slow for one week

Hello !

I've been experiencing some problems with Premiere Pro 2020 for about one week. I was working on a project, everything was fine. Then I wanted to add titles, the same I used in my previous video, so I made a copy/paste from one project to the other one.

And now the application is very slow. Not the functions themselves but how the video runs. I deleted all the copy/paste titles to make new ones but it didn't change anything. Then I reinstalled the previous version of the app (from Time Machine) because I thought it was because of the recent update. It's better but not as speed as it was before.

Do you think there is something wrong with my project ? How can I find what the problem is ?

Thanks by advance for your help !