Tooltips not working as expected

I'm testing v10.0.3 and the tooltips are working fine. When do they get displayed? I got some field record labels, which are truncated (added ellipsis, e.g. Company Name => Company N...) and on some fields the tooltip doesn't show up even if the field is truncated.

The only alternative I've found was to disable the Tooltips at all, but I'd like to use the Tooltips.

Any suggestions? Tested with latest Edge, Chrome and Firefox