Symptoms
For a specific form and a specific state on the form, every attempted to edit and save a rule (clicking the OK button) would fail. The developer tools (F12) were tracking the following error message:
Invalid XML:
<!DOCTYPE html>
<html dir="ltr">
<head><title>
K2 Designer - Powered by K2 blackpearl
</title><style id="ctl00_styleImports0" type="text/css">
@import url("/Designer/Styles/Platinum/Css/fonts.css?_v=4.15060.15272.5");
@import url("/Designer/Styles/Platinum/Css/buttons.css?_v=4.15060.15272.5");
@import url("/Designer/Styles/Platinum/Css/errorPage.css?_v=4.15060.15272.5");</style></head>
<body>
Diagnoses
I found this:
http://code2care.org/2015/synchronous-xmlhttprequest-main-thread-deprecated-detrimental-effect-end-users-experience/
Which led to the hypothesis that ne of e process threads from the browser session was bad. To verify this we tried editing the rule from a browser session on the K2 server directly and that worked swimmingly. We then tested an incognito browser session from the client machine and that worked swimmingly too.
Resolution
Clear the browser cache and then launch a new browser session.
