Taste buds are very funny creatures. In the beginning when our taste buds are getting back to normal it is not uncommon to go through this phase. For folks who claim this is bogus, well carry on.
As Gooddog stated, many recipes cannot be dbled without it affecting the final product. Since we are "cooking" juice, cooking applies here as well LOL. Many recipes (cooking) cannot be dbled etc... and there is no difference here. Often the recipe needs to be adjusted for larger quantities, not much mind you but some.
Once our taste buds have fully recovered from being more or less dead, our sense of taste is pretty much were it should be. What alters the flavour is often what we have eaten or ate. Onions for example (don't ask me why) will often manifest itself the following day. That being said, we also become (our taste buds) accustomed to our liquids and the flavour seems weak. Switching to a different flavour for a couple of days and then vaping the previous liquid will often lend different results. It is akin to a menthol smoker, who after a prolonged periods of smoking menthol, doesn't really taste the menthol any more, but still senses the difference in TH, compared to the same brand of un-mentholated cigs.
This hopefully explains what could be happening when all things are equal e.g using the exact same flavours e.g the same bottles of flavouring. Introduce a fresh bottle of flavouring because the previous one was empty, and this may indeed alter our perceptions, but should not alter them significantly.
IMO it is either we have been accustomed to the flavour and no longer taste it, or if we created a larger batch and, the flavours may need to be adjusted accordingly.
