Sometimes on freemarker errors in page/component scripts the right hand ActionBar has no Actions anymore.
I have seen this also in trainings.
Also other support cases were opened with this problem.
But we were never able to break it down into a reproducible situation to investigate into the bug.
Now a customer was able to provide an exact situation and code to reproduce it.
I can't add it here as it is customer code (SUPPORT-4885).
His example is working on missing html head&body markup.
But it also happens on certain freemarker errors, most likely having the same root cause.
I tried also with no html head&body markup and producing errors, but the bar didn't disappear.
So its some sort of combination triggering it. Its not just not having "html head&body markup".
See linked support issue.