Hello!
Is it normal, that in IIS Logs there are records with response code = 500, sub-status = 19 and win32-status = 64, when a client does not get whole content and TCP session is disconnected? I think it should be 206 response code.
For example normal request (485658 bytes - normal size of content):
2018-12-17 08:47:37 W3SVC4557XXXXX node32 192.168.0.173 GET /games/crossword/ - 443 - 99.186.5.38 Mozilla/5.0+(iPhone;+CPU+iPhone+OS+12_1_1+like+Mac+OS+X)+AppleWebKit/605.1.15+(KHTML,+like+Gecko)+Version/12.0+Mobile/15E148+Safari/604.1 https://example.domain.com/category/puzzles/ example.domain.com 200 0 0 485658 2781 1293
Request with error (204265 bytes - part of content):
2018-12-17 02:30:44 W3SVC4557XXXXX node32 192.168.0.173 GET /games/crossword/ - 443 - 174.109.27.106 Mozilla/5.0+(Linux;+Android+6.0.1;+SAMSUNG+SM-G900A+Build/MMB29M)+AppleWebKit/537.36+(KHTML,+like+Gecko)+SamsungBrowser/8.2+Chrome/63.0.3239.111+Mobile+Safari/537.36 https://example.domain.com/games/crossword/ example.domain.com 500 19 64204265 3872 79