[chrome 49 (2016-03-02)] Missing Tabber in backend Edit item

One of my editors (works still on Vista, with latest version of Chrome (49 for Vista)) has trouble with new FC 3.3.1.5 version, in the sense that he can no longer see in the backend Edit item page all the tabs Description up to Permissioin (with all content). Other users have no problems.

There is an error in the console of his browser complaining about tabber-minimized.js:
Uncaught InvalidCharacterError: Failed to execute 'contains' on 'DOMTokenList': The token provided ('tabberheading hasTooltip') contains HTML space characters

If I replace a previous version of this file he can see all tabs again.

Any idea what might be wrong (apart from him working on an old unsupported OS)?
Thanks in advance,

Folbert

Hello

is this user using a different language ?
is this user using a different WYSIWYG Editor ?

Language and editor (JCE) seem default, same as other user with exactly same profile (but different browser/OS).

is it in same computer ?
did you clean cache ?

No, on a different computer, this user cannot upgrade or change to other browser. I have seen via Teamviewer, his problem, reported here, cache was cleaned. Other user (me) am on modern browser version. I did not yet clear cookies for this user. Meanwhile have asked him to try with the latest version of tabber-minimized.js which (by my edits) avoids the classList.contains construction (which seems to cause the error)

if we can't reproduce problem difficult to debug ...
i use flexicontent in more than 20 sites in 3.3.1.5 and i didn't see this problem before