In true GI stasis, soon gas becomes involved as the bowel's contents start to ferment without being moved along. The gas-related pain becomes rather visible. They will be reluctant to move, lay in weird shapes (to try to ease pressure from their bellies), grind their teeth, may seem lethargic and may breathe rapidly. GI gas pain is extremely painful to bunnies, and one of the rare cases where they can no longer hide being in pain. If none of that is the case in your rabbit currently, and if she has regular and normal-shaped poops, then I think she currently is not in stasis. In true GI stasis, no poops would come out and gas buildup will become a problem real quick. If I read it correctly, you have been force feeding for an extended amount of time, in stasis one would have expected a load of other problems at this point.
So if I'm reading it correctly, your problem is mostly that the rabbit stops eating by itself, correct? Other than that, she has no bloat or gas episodes, no obvious pain-indicators (like what I just described), and behaves normally otherwise?
If that is the case, imo that rules out GI stasis and it sounds like you should look for other causes. Dental is a possibility, if chewing is causing her pain she will eventually stop eating. You might see improvement on properly dosed metacam in this case, though be warned that any underlying dental cause will not go away on its own and needs to be investigated either way.
Other options that come to mind, since you also said she had something else bacterial, is ear infection. If an infection is growing inside her skull, this discomfort might make her stop eating and cause lethargy at times. As the pus inside the inner ear expands, neurological symptoms may appear. Chewing might cause additional discomfort in the skull, which could be another reason for them to stop eating.
E.Cuniculi is a tricky one, hard to diagnose through tests and sometimes silently working already in your bunny. Luckily, the medicine (panacur) is very very well tolerated by rabbits and can safely be given either way. Proper treatment duration is 28 days of panacur at the appropriate dosage. Many (if not most) rabbits carry E.cuniculi within them from their early youth with no problems. When the immune system is weakened by another infection, it can flare up. This has happened in my 12 year old rabbit who had an airway infection which was treated by antibiotics however was quickly followed by severe neurological symptoms from E.Cuniculi having grabbed their chance. My bun made a full recovery on panacur/meranox (fenbendazole). One of the early symptoms of E.cuniculi is "unexplained weight loss". Visible neurological symptoms such as head tilt, ataxia etc, mean it is relatively far progressed.
Bottom line, I think something other than GI stasis is going on. In the meantime, you're doing a good job on the syringe feeding - keep that up, and try to keep her weight stable!
