Hi
I had a crash of Sigil 0.9.13 yesterday, but it was the Complete edition of Stephen King's Dark Tower - all 8 books in one epub (in German - maybe in English there are more?) which has 7.244.659 bytes on my HD. That's my 'killer-epub'
At the same time I had a second instance of Sigil running with a 'normal' epub which wasn't affected in any way.
With all 'normal' books it works very well and fast for me(Win 10 V 1803, AMD-FX 8350 at 4 GHz, 32GB RAM)
Just report it for completeness-reasons...