This was occasioanaly reported with 8.3.1. and 8.3.2 and was addressed with the 8.3.3 release, however if you are unaable to upgrade or experience a freeze for whatever reason it may be useful to know that in all versions the project is 'unpacked' to;
(You can find this hidden folder by typing %AppData% in Windows)
There will be a large amount of files in here, all worksheets will be CSVs and you can find PML model code, NCA core ouputs etc. as .data.
This information should help you recover quicker from a freeze or crash, if you don't have a more recent saved copy of the project to hand.
I woudl be very cautious in changing this when you have a 'live' project open; you will notice that it gets cleaned out upon exiting Phoenix normally.