You're totally right it's because I use a discrete measure, I already figured this out ... but my concern is: it was working before...
I showed to some end-users the double-click zoom trick and now without changing anything in the worksheet but just upgrading tableau version it is not working anymore...
Anyway, I did some search and found that the following idea https://community.tableau.com/ideas/1043 may have led to this new behaviour.
If you look at Sean Boon post on 22-FEB-2016, he seems to confirm that this will be the new default behaviour (no zoom when a discrete measure is used).
"(...)Well, since it's a birthday, maybe there ought to be some presents . We have added a feature that is currently in Beta for 9.3 that will adopt the same behavior that we have in desktop, which has been in desktop for a little while now. For sheets being rendered in the browser on Tableau Server, double-clicking in a plot that has just a single quantitative (continuous) axis will no longer zoom on double click. You don't have to do anything to configure it. It is just the new behavior. (...)"
I'm quite disapointed I would have expect that the solution retained would have been the same as for maps: an explicit option to disable Pan and Zoom...
Changing a default behaviour is quite different than offering new options.
This is excellent sleuthing, Dominique! I'm sorry the new behavior doesn't work like it did before...
I hope you'll be able to find a suitable work-around. If not-- you're in the perfect place where there are boatloads of people smarter than me that can help you out!
Wishing you the best!