Libreoffice 'Not Responding'

Hi, I’m having difficulty with my Libreoffice programme and would appreciate some advice. Explanation: - I’m using the programme to write my third novel. I’m in the first draft editing stage and have the original as a complete document and to aid the editing process have broken it down into sections. As I complete each section for changes I copy it (up to six pages in a block, give or take) go into the Master and try to paste that updated section in place. When I first started this it was fine but now, as I’ve got further into the book, each time I now do this the programme freezes and I have to do a recovery (VERY SCARY). Is there a way to do this? I’ve tried copying a page at a time but get the same result. Peter.