Here follows an extract from How Big Is Too Big for a Microsoft Word Document? . Could it be relevant to the files you are working with?

"Word documents that are half a gigabyte are going to be extremely difficult to work in, especially if the bulk of the file contains images or videos. However, a lot depends on your system resources, and whether your computer is capable of working with files that large.
It also depends on Word itself. While the program is typically stable for general use, you might find it significantly less so if you try to work in or save a file of a substantially larger size than usual."


Do you have plenty RAM and an SSD (not an HDD), processing power and a decent graphics card?