I have a 5 bulb decorative fixture in the dining room. The bulb type is Candelabra and there is only 1 on/off switch for the light. When I run more than 3 LED bulbs on the fixture, the first 3 light up but numbers 4 and 5 stay dark. I have swapped bulbs around and even tested them in different fixtures, all bulbs will light up. I even can get the "dead sockets" to change depending on which bulbs I put in first. I also can install 3 LED bulbs and 2 incandescent, and all 5 will light up.

Let me start by saying I don't know.

But, I just did some reading on LED bulbs a few days ago. One of the negatives about LED bulbs is that they are sensitive to over voltage. That might explain why the use of a couple incandescent bulbs would make the LEDs function properly. The incandescent bulbs causing a slight voltage drop.

Suggest replacing the LEDs with different brand and returning the ones you have as defective, if possible. Otherwise use a couple incandescent bulbs in the fixture.