I believe this is a vestige from the pet bomb glitch, as the same issue happened after the first fix attempt. When I fire my gloves as an engineer, my rover pet disappears. It's still equipped but doesn't show up in my zone. The same thing happened with cats and turkeys a while back.
I also think that the pets with special effects (jets, dot trails...) have some clash with gloves, as the vular pets didn't have any issues (not sure about the puking vular).