Glowberries grow VERY slow on vines!  I have sat in an area with it loaded for almost 15 hours real time!  Almost ZERO glowberries have grown, and some of the vines aren't grown past 1 block length!  All I have are vines with no berries and over +15 hours of real time with the area loaded!

Steps:

1. I placed vines by hand on the bottom side of blocks.
2. I sat in an area and waited for them to grow.
3. After more than 15 hours of real-life time has passed, there are only vines and no glowberries!

I believe this could be caused by a combination of MCPE-145612 (50% of ticks discarded), and constant lag that plagues realms and causes ticks to not happen.