Thank you. So, we have determined that you computer is fully capable of handling large scale projects so it’s not within any limitations of VRAM and graphics that would cause your project to load slower. You have also stated that this does not happen within a new project. At this point I believe you may be correct in your assumption that your project has become corrupt.
I highly recommend starting with a new project. If you have an older version of your project that you can fall back on this may be your best option.