Some of you may observe this error on your Chrome browser while accessing your site or content delivered via Akamai.
This is a known issue and is seen mainly on Chrome v64+ (Version 64.0.3282+) so far. The issue is caused by invalid characters in the ‘Akamai pragma response headers’ which means that only users who are sending Akamai debugging Pragma header (specifically ‘akamai-x-get-extracted-values’) on Chrome v64 will see this issue.
The assumption here is that the header validation may have gotten stricter in Chrome in v64. This is causing H2 protocol issues anytime the "Pragma:akamai-x-get-extracted-values" request header is used and the value of any of the "x-akamai-session-info" response headers contains an invalid character. Akamai engineering team is currently working on substituting certain characters to prevent the leakage of illegal header values.
As a workaround, you can disable sending Akamai debug Pragma headers on Chrome or use a different browser to continue debugging Akamai features.
You can find the official KB article here.