@TraceyStudios
Please do post back in a bit with an update on how it is all going for you - it is tentatively good that it is tentatively good - hopefully things will remain more stable.
Just a thought - I think I remember seeing that some folks had some issues opening older projects, due to plugins (might have been 32-bit, look-ahead buffering, that kind of stuff). Perhaps you could try opening one of your problematic projects in Safe mode and not loading the plugins - then load them in one at a time to see if any of those are contributing to any weirdness. And, if a 64-bit version of any of the plugs exists, try changing those from 32-bit to 64-bit and see if that helps too.
Certain plugins use something called look-ahead processing, or look-ahead buffering, and these can put the whammy on things, from what I understand, depending on how it is used in a project. Perfect Space is one such plugin.
For one of your problem projects, can you please detail which plugins are used, and whether or not they are 32 or 64 bit? That may be helpful to know.
Bob Bone