Problem launching WF5 on ipad

Hi. I have an html5 site with a workflow that is accessed via a button in the toolbar. On an ipad, using Chrome browser, I can't launch the WF. I get the generic message: "The application is experiencing issues while performing this operation".

Oddly, I have the same WF configured to launch via links in the maptip for several layers and it works fine.

Also, with safari browser, the WF can be invoked from the toolbar button. And it works fine on other devices invoking from the toolbar button.

Is this a known issue?

Running essentials 4.12 & viewer 4.12.2.

Thanks