Hey T3 developers and fellow users,
the recent Joomla! update to version 3.6.3 changed some of the javascripts for module editing. This seems to have broken the frontend editing of modules for T3 template with Bootstrap. The dropdown for the module positions remains empty with no options to choose any position. If you save the module, the module is set to an empty module position and thus does not show up in the frontend anymore. This behavier can also be seen with t3_bs3_blank, but not with t3_blank. Only Bootstrap dependent tempates seem to be broken. I did clear my browsercache serveral times and testet it with Firefox and Chrome. Same result.
I tested this bug on two different systems on two different servers. If the Joomla! is version 3.6.2, you can choose the module position with a T3 Bootstrap template. With Joomla! 3.6.3 and a default template like beez3, you also can choose the module position. But if you change to a T3 Bootstrap template, the dropdown for the module position is just empty.