I started a scan yesterday and for some reason it decided to take hours and hours instead of minutes. I had to leave it running overnight - and eight hours later it was still only a touch over 50% complete.
Yesterday evening I couldn't use emby at all. All of the images had gone (I guess because the scan had completed) - I just got black rectangles everywhere (in MBC, ET and the server). Note: I have all my metadata and images stored locally with my content and download artwork and metadata is turned off.
I was on 3.0.5851.25344 and this morning I've updated to 3.0.5854.21433.
Today I've turned off chapter extraction during scans - restarted the scan (again), and it's going quicker - but still slow. About 5% in 20 minutes, so at least it'll finish today.
Now it seems any content that has been scanned today does not have chapter images, even though everything did have chapter images previously.