Breaker trips when fixture is not screwed to metal box

The scenario is, I think, rather simple, but I’m not 100% sure of the answer. You have a very simple circuit. A breaker feeding a black wire to a switch, then to a LED light which is mounted to a metal conduit box. All of this is connected using EMT, so it’s grounded. The LED fixture doesn’t have a ground sire, per se, it doesn’t even have a spot to attach a ground wire. The LED is connected to the switched side of the black wire, as well as directly connected to a white wire. Just two wires to the LED fixture.

When the LED is screwed to the metal box (grounded) then it appears to operate correctly. When I drop the LED fixture to examine wires, then try to power the circuit to test it (in preparation for adding more lights to the circuit), the breaker immediately trips. It works fine when the LED fixture is screwed to the metal box. But if it doesn’t contact the metal box, it trips the breaker. No GFCI involved, it’s just a normal breaker.

Is it using the grounding as a neutral? I feel like this may be an issue, or maybe it’s ok and I just didn’t understand it. I can tell you the building is relatively new construction within the past couple years, and was professionally done, no DIY work in the build.

Edit: Yes, the wires themselves look good. They are connected to the LED using screw terminals. And they are connected to each other using push connectors, rather than wire nuts.

It’s just perplexing that the fixture works when screwed to the metal box (which would ground it). And trips breaker when not screwed to the box. As if it is getting its neutral through the grounding of the conduit

Reply to commenter: Well, I will need to look to get the model info on the LED. It’s a fixture and was installed by an electrical contractor who did a whole building. For what that’s worth.

Also, there’s no GFCI issue, as there isn’t one in the circuit. It’s a regular breaker. And the previous comment is backward: it only works when connected to ground. (Previous commenter thought it was not working when connected to ground). Fact is, when not connected to ground, breaker trips. When connected to ground, it works.

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If I have the fixture hanging down, not contacting the box, it is supported by the hot wire and the neutral weird which are connected to the terminals on the fixture. It’s a very small, light weight fixture, a few ounces maybe. If the fixture is hanging down, there would be no way to ground it with a wire, because the fixture itself doesn’t have a grounding lug. But it obviously picks up ground when it is screwed to the box.

Of course I would only have it hanging for a few minutes while I was wiring other fixtures and testing them. Now that everything is out together, it works normally. It just seems odd to trip the breaker and I was wondering if it points to a fundamental wiring mistake originally in the building. My sense is that the fixture should work normally without a ground…such as when it is hanging and not screwed fo the box. It wouldn’t be advisable or safe for long term use, but it should function and not trip the breaker. That’s my sense, and why I was concerned about it.