BLUF- Your juice is fine, could have been many factors.
GMO, I am an well I can not say it here as I typically say, but a very pointed person. The Brother Banyan is not my thing, there is something tart in there that I just do not like. I know lots of people rave about another juice vendor, I will not name them here, but it just had a chemical taste to me. I wound up selling it with lots of other juice that I did not like, the recipient loved it. Tastes are subjective, you are not going to be able to please all of the people all of the time.
Also as Schnarph said vapors tongue gets us all at one time or another. I have ran your juice though carto's, tanks, dripped on 510 attys, although I will never ever again get one of those lol, RDA's and they are wonderful and flavorful. I have only had two of your juices that I did not like, and they were both juices I had high hopes of liking.
Now the Rwhy4 I thought I would hate, well it is now one of my favorite juices, as it ages it just seems to get better too.
They might have decantered the juice into another bottle, or another thing is did they use a syringe to transfer the juice? That rubber can wear out in time and create a flavor as well.
To be honest I would not loose much sleep over it I know I have sent at least a few people your way from some forums, one I know for sure has placed an order. She had a reaction to a 100% PG juice, I have been there done that with ulcers in my mouth, doing PG and cinnamon most likely did not help but

I like that sometimes and might have to whip some VG with serious heat up soon.
I have had a ton of stress on me lately, and hate to admit I have had a few smokes here and there. Nothing like before but sometimes after I vape a bottle of 18mg sky in 8 hours and find myself still fitting, I need a smoke.