Trancing induces tonic immobility (TI), which is a built-in reflex rabbits have. Entering that state and its physical characteristics (i.e. looking relaxed with non-moving limbs) is a means for rabbits in the wild to escape death, as a last ditch effort. If they cannot escape, the best chance for survival is to act “dead”, so the predator loses interest.

Because TI has such a function, being put in that position both intentionally and unintentionally still means the rabbit’s stress levels and heart rate skyrocket. For rabbits who are generally of weaker health, they can actually die if tranced too often or for too long, because their heart gives out. For healthy rabbits, it may not kill them, but it is generally considered unethical to force them to experience that discomfort. It’s synonymous to someone forcing a panic attack on a human. Humans with high anxiety forced into a panic attack can have terrible consequences. Humans with no history of anxiety or general health woes may not die from a forced-on panic attack, but during the moment and afterwards, it is definitely uncomfortable and can be traumatic.

There are times a rabbit will roll over onto its back, but there are two distinct scenarios, and this is dependent on the head/chin level, as compared to the chest. A rabbit can accidentally trance itself if it rolls over and its head drops below its chest level. Even if the rabbit did it “on its own”, it’s tranced and that’s traumatic. Other times, rabbits will lay on their back, but most likely it’s accompanied with a body curl of some sort, where their head isn’t actually below their chest, so the appearance is still somewhat “on their back”, but they aren’t trance (note trancing a rabbit and then curling its head up is still a trance). The difference is slight, but the consequences are much different.

Exactly what Wick said.
There was a case where a groomer put a bunny on its back to make it easier to cut its nails… while yes, it looked relaxed and wasn’t moving – what Wick mentioned above was happening inside the rabbit and he went into cardiac arrest and died.

Quite simply, rabbits do NOT enjoy being tranced.