We have set-up a partner community for our customer where we have overridden the "new" button on account with a visualforce page (for "classic") and a lightning component (for "lex").
In the "classic" community this works perfectly, in the "lightning" community the button is not visible as soon as the override is activated.
For full license users (ex: administrator) the button remains available and is working as expected, both in "lex" as in "classic" UI.
Do any of you have an explanation for this behavior? And preferably a solution as well :)