[Edit…
@shooj please read this - IMPORTANT UPDATE - WORKAROUND for CDN DOWNLOAD ISSUE, but not a solution for most Zwift users:
I disabled the “Web Proxy Filter” feature that scans HTTP requests on my firewall (I work in IT) and no longer get the Z117 error and Zwift game has updates to 1.0.100278.
My diagnosis is that your Cloudfront CDN is sometimes returning content in a way (‘chunked encoding’?) that the Zwift user’s firewall, proxy, security client etc. does not like and it is being blocked. This is causing the truncated file download and thus the checksum error
Search up this from fastvue, which may be relevant: “How To Solve “13 The Data Is Invalid” Error in Forefront TMG” which suggests:
This error occurs when the destination Web Server is using Chunked Encoding but it is not passing the correct TransferEnconding header.
I am fortunate to work in IT, so can update my home network to workaround this apparent Cloudfront issue. Zwift needs to please work with Cloudfront to resolve, as many of your customers will not be able to.
/Edit]
Original reply:
@shooj hope these firewall logs help. I see the Zwift launcher making lots of successful HTTP connections, then a mal-formed one, which I am assuming relates to the checksum file download issue.
I am trying to add firewall logs to this reply but your annoying forum says I cannot include links, so have had to re-format some of the log content below, you can still see the issue.
Firewall logs: Successful file downloads are made, then this:
Failed Connection Attempt 02/01/2022 08:26:40
Log type: Web Proxy (Forward)
Status: 13 The data is invalid.
Rule:
Source: ( x.x.x.131:0) ← This is the IP of my Zwift PC
Destination: (server-13-227-172-3.lhr52.r.cloudfront net 13.227.172.3:80)
Request:
Filter information: Req ID: 0c256a23
> Protocol:
User: anonymous
Additional information
Client agent:
Object source: Processing time: 0
Cache info: 0x0 MIME type:
Later on a successful connection:
Allowed Connection 02/01/2022 08:26:52
Log type: Web Proxy (Forward)
> Status: 200 OK
Rule: Web Access Only
Source: Internal ( x.x.x.131:0)
Destination: External NIC (server-13-227-172-3.lhr52.r.cloudfront net 13.227.172.3:80)
Request: GET [13.227.172.3] gameassets / Zwift_Updates_Root / Launcher_ver_cur.xml
Filter information: Req ID: 0c256a4f
> Protocol: http
User: anonymous
Additional information
Client agent:
Object source: Internet Processing time: 47
Cache info: 0x58800000 MIME type:
Later on the firewall session with the invalid request times-out:
Failed Connection Attempt 02/01/2022 08:28:51
Log type: Web Proxy (Forward)
> Status: 1460 This operation returned because the timeout period expired.
Rule: Web Access Only
Source: Internal ( x.x.x.131:0)
Destination: External NIC (server-13-227-172-3.lhr52.r.cloudfront net 13.227.172.3:80)
Request: GET [13.227.172.3] gameassets / Zwift_Updates_Root / Zwift_1.0.100278_e38ad30c / assets / Noesis / Blend_Data / noesis.wad
Filter information: Req ID: 0c256a17
Protocol: http
User: anonymous
Additional information
Client agent:
Object source: Internet Processing time: 131766
Cache info: 0x58800000 MIME type: