Sorry for the long post. My family's Rottweiler, Rocko, is about 3 years old and recently he's been displaying some pretty concerning behavior. Pic above is from 2 days ago.

We keep him mainly outside in our yard along with our other dog and they've been good up until this month.

The only other problem he's really had is frequent eye mucus but that was just because of dust. 

We were mostly focused on our other dog because she had given birth the day before, so we didn't notice anything off with Rocko.

On April 6, my brother found Rocko unresponsive in his kennel kinda flopped over. We didn't know how long he was like that for. However, once my brother tried helping him up, he was up and walking. From there, he was visibly weak and. He then just circled around the yard a bunch of times, bumping into things and not responding to his name. He ate and drank water to an extent when we offered it to him though. Usually he'd lick his bowl clean, but he couldn't put his head down long enough without stumbling forwards. After a while, he didn't even want a treat when offered, which was unheard of for him.

We took him to the vet later the same day and they said it was his liver. They said it was either poisoning or a liver shunt, but they settled on treating him for poisoning. Up until now we have no clue what could've caused that because he wouldn't have had access to anything harmful. Plus, our other dog has been completely fine up until now, so I don't even really know what it could've been.

  
They kept Rocko at the vet for a few days, just to monitor him and flush out his system. By day 3 they said he was getting better and when we visited, he looked better. However, he sometimes didn't want to eat there. We chalked it up to him just being uncomfy around strangers, so we brought him home on the night of day 4.

Honestly, he was doing much better. He wasn't his usual self, but he was slowly recovering. We fed him more protein + some powder we had to put in his food for a week. His barks were pretty weak at first but after a few days, they were back to normal. He also got kennel cough from the vet, smh. But that cleared up a few days ago and he was doing so good up until a few hours ago.

We heard him breathing pretty loudly in his kennel. When we went out, he wasn't responding to his name and just lying down. My brother pulled him up a little and then he was immediately walking.

  
He was circling the yard again and not responding at all to his name. The only difference to the time we took him to the vet was that he wasn't stumbling. But he ate and drank too. This was relieving until we noticed that he was circling the yard and doing the same thing each cycle. He walks around, drinks some water from his bowl, then repeats. He sometimes switched up the places he'd go, but it was mainly that cycle.

And that's it. We let him get some fresh air for a little while before putting him back in. 

I feel like it's something neurological, but the vet didn't say anything about that, so I'm just super confused on what's wrong with our dog. So I'm seeking a second opinion before we take him back to the vet, just so we can discuss with them what more it could be. 

Please share some advice on what it could possibly be. Thanks in advance.

Not sure what's wrong with our Rottie