Now i think i'm following, you're putting a macro in the Container TItle section, and in your Webpart Container you have {% ContainerTitle %} to pull it in but it's not rendering the macro.
That's because Kentico's Macro resolving behavior changed, it no longer by default recursively renders.
On your Webpart Container, put this:
{% ContainerTitle |(recursive)true %}
That should tell it to recursively render any macros in the ContainerTitle