squeaking sound - help!

So, Aki has a history of having bouts of stasis from time to time. She's 8 and her guts don't seem to be as efficient as they were before. I've had a few suspicions in the past three days because she didn't come running for a vegetables three days ago and neither did she yesterday (but the day in between she did). I saw her eat her pellets with gusto yesterday morning and hay during the day, I'm almost sure some of the poops that were on the floor were hers (it's hard to tell, because she lives with another rabbit and poop is poop but hers tend to be a bit smaller). And this morning, she was hunched in her litterbox, not eating and in pain. So, nothing new under the sun - I gave her metacam and Emeprid which is generally how I settle this. But giving it to her with a syringe, I heard a weird noise while she was eating (swallowing?). I don't know how to describe it except that it sounded like nails on cardboard. Kinda squeaking? It was so weird I wondered if she was really making it. I took her to the vet immediately. Here, I have to say that there is no real rabbit specialist where I live. I live alone, know no one in the town and don't own a car. This vet is the best I have found.
He examined her teeth and found nothing. She had perked up a little bit after the metacam, but still no eating or pooping. He said he could feel a string of poops in her stomach but found no blockage , suggested she had eaten too much parsley. It's true the rabbits had a lot of it during the past three weeks, and I suspect she didn't eat as much hay as she should have as the bag I opened a few days ago didn't smell great - I saw her eating some and her husbunny seemed fine with it but he is a lot younger than she is and not as picky. He found her to be a bit deshydrated, and she was standing next to her bowl of water but not drinking several times this morning.
He told me to keep giving metacam and Emeprid, gave me some fibreplex (a paste which is supposedly rich in fibers and that she took when she had ileus one year and a half ago). He said I could give her water with a syringe. I came home and gave her a bit of water as well as the fibreplex. I head the weird noise again, which really worries me and which the vet had no explanation for. She is making no weird noise at all outside of the time when she is swallowing (munching?) what I gave her with the syringe.
Of course, coming back home I found out the assistant had also given me the wrong metacam (the one for dogs and with no syringe)... sigh...
I'm leaving her alone for now with grass, water and hay but I'm really concerned.
Does someone know what that could possibly be?

She could have something stuck in her throat that is causing the squeaking noise. Or something more serious would be a mass partially obstructing her windpipe. If it was something as simple as a piece of hay stuck, it could resolve itself in a few hours time with lots of hydration. If it doesn't, you may need to investigate the cause further, possibly with having xrays done.

Is the dog metacam different than what you would normally be given? Here in the US it's the only one there is, though it is honey flavored.

Thanks! I gave her small 1ml syringes of water throughout the day to help with the deshydratation (it was really hot too yesterday) and the noise suddenly stopped after about 12 hours! So I guess she had something stuck somewhere... could it really have been a piece of cardboard? She shreds a lot of cardboard boxes... Or a piece of hay? Anyway, she ate two pieces of lettuce this morning and she ran away when I went to give her her meds which reassured me because she looked really bad yesterday - she seemed to have difficulties swallowing and she was scarily unresponsive, letting half of what I was giving her dribble out of her mouth and staying hunched in her litterbox. But I guess if she had something stuck in her throat and that she was deshydrated, it could have been the cause.
Normally, we give Metacam for cats as the dosage is lower (it's 0.5mg/ml instead of 1.5mg/ml). It bothered me mostly because I was using the metacam syringe which doesn't mesure in ml, but I ended up finding a website where they explained how to convert it in ml so in the end it's fine, I'll just have to give a smaller dose.