I think I have misled you a little. Thumper hasn't looked at death's door since he was a baby.
I've found rabbits to be incredibly intelligent. They use different senses to us - relying much on smell & hearing, rather than vision as we do. They have different priorities, not only as prey animals, but also were they to show any physical weakness it could result in a "challenge to combat" from a fitter rabbit lower in the social heirarchy. Loss of place would mean loss of better grazing & burrow rights. So their instinct is to hide illness until they can't do so, for 2 reasons. The one thing rabbits won't do is "pretend to be ill".
They are intelligent in learning rapidly when it's important to them! Thumper learned the names of his herbs, the 3rd. time I used them. 3rd. dental - & he knows what's coming.
What I think may be happening with Ginger is that when he gets spurs, he's learned that he has to chew less or he'll cut his mouth, & not be able to eat at all.
Bun's have a problem. They have to chew a lot of fiber which gives them no nourishment, or their guts stop working. If they use all their chewing capacity on fiber there isn't enough left to eat nutrients for glucose. They can't use "fat" stores like we can. If they eat enough nutrients, there isn't enough fiber to keep their gut moving.
I've watched Thumper desperately trying to get the balance right, & not having enough "chew" to do it. He even cuts down on energy expenditure (need for glucose from his food) but it's very subtle, he just doesn't come downstairs to investigate a visitor, or plays fewer running games. I would guess that Ginger tried to have a day of eating fiber to get his gut to work better, & just didn't manage to get enough nutrient in. Or needed a day to
to allow a painful, but not ulcerated mouth to settle down. Bless him he's doing his best, but can't win.
With Ginger losing weight easily, he's got an additional problem.
Poop output is the best index of fiber intake. We have big probs with fluid intake (Ginger probably doesn't) Increased urine turbidity is a warning sign, poops like rocks & wee output less than 4cc = dental NOW. Hungry (asking for food early) rushing to dish but then leaving 1/2 of it = Metacam & Dental in next 2 days for us. I think you will have to find the subtle signs for Ginger.
I ensure that Thumps has a meal before we go for a dental. I'm convinced that stress control as far as possible is important. I really wish we could reduce the stress of travel for Ginger. 40 miles is necessary and a long way. All advice appreciated - perhaps discuss with your vet.
I always leave his favourite toy rabbit, & a smelly gardening jumper of mine (I'm his companion "rabbit") when he's admitted. It's just to relieve the stress of being in a totally strange environment by giving him something familiar to smell.