I've heard that all film manufacturers are using 120 backing paper from the same source, and I don't want to risk a ruined shoot.
I keep seeing that in these threads, but I am way less than convinced that is the case. Even if it is, there is the paper itself, then there is coating and printing on it, which appears as though it is a two step process. There are also radical differences in the surface finish of the papers from various film makers. Each film maker has a different design of numbers and lead-in symbols. Some films have the film type printed directly on the backing paper, some don't. So if all of that is literally coming from one place, it's being done to some sort of contracted specification (and thus could vary between "brands"). I think it's more likely that either the film producer or an intermediate contractor does some of the middle steps which means potentially different results between brands.
I had some 400TX from a batch number that was flagged which I had yet to use, but it was bought for a major auto tour, so I contacted the aforementioned Mr. Mooney and he sent replacements. I shot a number of rolls of the replacement film on my trip, but also interspersed some HP5 to spread the risk. All was fine, and this stuff saw temperatures well over 100ºF in Arizona along the way. Admittedly those temperatures occurred under very low humidity however -- that's another potential variable.
At any rate, this year for some "photo walks" with a local group through local sites I've been to before and can easily get back to again, I have shot some of the original rolls from the potentially bad batch -- and not seen a problem. I know other makers have had the problem years back (before I was shooting any medium format) but I have used Delta 100, FP4 and HP5 from Ilford and still shoot a fair amount of Acros from Fuji, as well as a minor sampling of color films a few years back, without seeing this problem.
I no longer shoot color film, mostly because of processing expense and hassle (vs "other technology") but I have yet to see a problem with numbers on B&W. Admittedly, I have shot no recent vintage Tmax films, which seem to have been the leader in showing the problem.
I suspect (old retired engineering type here!) that the problem is a complex one in which specific emulsion chemistry, storage temperatures, humidity levels, and handling post exposure may play a role. The
Great Yellow Father has obviously made changes in their numbering, reducing the amount and density of the inked numbers. I would say a smart move would be to buy a quantity from one batch and try it a roll or two before traveling. If they're OK, go with it. But I would think if you're going to spend two months in some sort of tropical rain forest environment, some 35mm/sheetfilm/electrocuted bits as backup might be wise. I also suspect under those conditions that has always been a possibility.
There's my rambling 1.3 (after tax) cents ...