I grow babaco and chamburo, and have done a lot of research on vasconcellea. I have seeds from 7 species that I am trying to germinate. Most germinate only in laboratory conditions.
The problem with papayas lies in the root system, once that is damaged root rot sets in. I have a solution for every problem of papayas in containers but I will not share them as it is my own research and invested years in trial and error.
To have a faster growth you need a deep container like 3 feet. Also your plants show signs of nutrient deficiency. A foliar spray containing microelements every 10 days will improve the appearance.
There is not much research on palanda. And who wants to go to the forest to pick up the seeds, he must be kidding. That is not a vacation to walk through jungle for 3 hours with snakes and other animals, especially to go there alone.
I know the exact location in case someone is so courageous and I asked many Ecuadorian friends to go to pick up some fruits, but they declined my offer. Those who have the plants you better preserve them. The forest where palanda is, will be cut in few years so it will become a extinct species soon.