Yes, I think that's very typical when you go away from home to regress. It does often work itself out when you get back, but since it hasn't, let's take a look at it.
There is a chance he's having a growth spurt. Typically there is one at 4 and 6 mo, but I know there were a couple LOs my DS's age that had one around 5 mo. And they don't always come right when expected, so he may be having one a little early. The other thing is, he's getting to the age of being about ready to start solids. He may just be more hungry. My DS is also a bigger baby (although slimming a bit), he was still around the 90th centile at 6 mo. He is EBF, but did start waking for another feed in the night from 5-6 mo. We started solids at 5.5 mo and I 'think' lost the extra NF a week or two later.
How did you go about losing the feed the first time? Can you add any more oz to his daytime bottles and reduce that second night one any more? What happens if you try to resettle him at one of the feeds? Are they habitual enough that you could try wake-to-sleep?