Excessive loading time from library

I open in Animate CC a .fla animation started in Flash CS5 with my old iMac under Sierra. I am now using a new iMac 27 inch running Catalina. I observe that the time to load clips from the library into the main scene is increased from 8 to 9 seconds, it was instantaneous with Flash and the old machine. It is a huge degradation. I haven't found a solution. What can I do ?

Jayceebee from Paris france