1/3 of the failures remain scraper bugs to be fixed - some are fairly trivial and are being hot-fixed in 1.15.1, some are more subtle and will be fixed in milestone 1.16.
The problem is that we don't when/where failures will occur.
As a reminder it takes anywhere between 6 to 20 days of crawl and compute to generate a zim file with 7M entries. It this happens at the beginning of the crawl, it sucks. If it happens at the end of the crawl, this sucks big time.