the initial version was 12.0.65.
The macros were inserted to the static html text area via the ckeditor.
Like I said, calling
ltlText.EnableViewState = (ControlsHelper.ResolveDynamicControls(this)); in the code behind was working for widgets (and still works when it's a webpart) up until the upgrade to v12.0.98.
I can solve the issue now by calling
ltlText.Text = MacroResolver.Resolve(Text);, it just means now I have to apply the fix to pretty much all my widgets.