Did you recently repot the plant?
It takes energy from the plant to close and open traps, if recently repotted, it would be
weak due to acclimation to it's new invironment and the traps may act funny.
I noticed that after potting a plant, the traps are sometimes inactive and will not shut
even if a live fly goes in.
Traps that got shut in shipping will either open half way, or turn black.
When the plant gets acclimated, the traps start to work but each one will open and
close a certain number of times, then it will die off and be replaced by younger ones.
“I yam what I yam, and that’s all, what I yam”~ Popeye ~