It's by design that if you set a layer to global, it overrides the objects on all the other layers with its own content. However due to the architecture of the editor the overridden layers can't be displayed on the other layouts, so their content will seem to disappear. This is still by design at the moment.
I can reproduce editor issues if you try to modify a globally overridden layer - the editor will prevent that and tell you to modify the original global layer instead. I can reproduce some cases there and I'll try to fix all cases of that for the next beta. However the OP alludes to a runtime error but does not specify how that occurs. Can you describe some more about that? Can you still get it to happen even if you pretend the editor doesn't allow you to modify a layer which has been overridden?