Problem rendering contents in Visual tab on Description field on JIRA 7.3.x

As stated in release notes for JIRA 7.3.x here, there is new Description field, developed in Atlassian Labs.

Now I have a problem with rendering contents on Visual tab, even though I have my content properly displayed on Text tab.

Quick workaround is just to try editing something on Text tab and Visual tab will properly initialise and render proper content.

Since I am just pasting some content on Text tab automatically (via Add-on), I would like to know if there is some additional actions like some initialisation, which I need to call after I pass content on Text tab, in order to Visual tab properly render it?