Long loading times and corrupted project files

I am using Captivate Classic Version 11.8.3.8 on a Windows PC and recently the project file crashes regularly creating corrupted files (about once a week). I developed a habit of saving the poject as a new file everytime I am working on it so I am not losing too much work but for some reason, a crash leads to almost all previously saved files to be corrupted as well even though I was able to open them before. Moreover, the project is quite large (700 slides, 600MB) and simple copying/duplicating actions can take up to 10 minutes, seriously slowing down the workflow.

I'd greatly appreciate some ideas what might cause that - is the project simply too large or could there be other issues with the program itself? Thanks!