Having problems with my Promenea

[Angurek]

Have you unpotted the plant to check the roots?

From my experience, members of this alliance start doing this when their roots have gone south and can no longer support the growths. I haven't grown this genus personally, but if it's anything like Zygopetalum, it probably needs to be kept evenly moist (not sopping wet or bone-dry). They also start shedding leaves if the ambient temperatures are not right. Try growing it under intermediate temperatures (with night temperatures that do not dip any lower than 55 degrees fahrenheit, and daytime temperatures that do not go above 80 degrees fahrenheit).