But actually this is Node Red behaviour, not directly ui-builder its self.
If a Node becomes invalid (due to other dependent Nodes being disabled for instance) - even on the same disabled tab
I think Node RED STILL errors out, despite the tab being disabled.
As an example, I just dragged an MQTT Node on to a tab (I didn't configured it), deployed = Error (to be expected), then disabled its tab, and Node RED still complains, despite many deploys after
If it happens on other nodes - a simple one to check would be the function node - then, as Marcus say's, that is a Node-RED "feature" rather than a uibuilder one.
Should be easy enough to get rid of any uibuilder errors though, there aren't that many things that would cause a uibuilder node to return an error.