Filling description using a behavior: cannot switch to text mode from visual

[Tim Nixon]

I have  a behavior that prefills the description on create of issue based on the scriptrunner documentation

If the user (on create screen) selects the pre-filled text (in visual mode) then deletes it, then switches to text mode the cursor disappears, if they switch back to visual edit mode it re-appears. If they start in text mode then all is well. Atlassian seems to think it is something in scriptrunner plugin

Is this a known issue?

jira=7.3.8

scriptrunner=5.4.34