I've had a problem with my neps (particularly a ventricosa red sitting on my desk) opening their lids early, causing a malformed tiny lid to a normal pitcher. Humidity is about 60-80 percent, and I have the required temperature drops at night. I've tried spraying the plant everyday, I've tried trays of water, I've even kept the forming pitchers in the shade and away from the sun. I've had few successes, and most of my pitchers still are deformed.
Recently I tried a last-ditch effort: I stuck some wet toilet paper over the hole between the opening lid and lip. Left it there for a few days, and when I uncovered it today, the pitcher and lid had grown together again, so the hole had sealed itself up.
Anyway, if anyone else has this problem, please try this out and let me know if it works. I don't know if it was a fluke or what. It does seem that as my ventricosa gets older it makes better pitchers, but as I said, this could be a fluke.