Can you upload a photo of your
Miniature Wax Plant (Hoya bella) so that we might be able to see the issue?

In your earlier post, you said it was peduncles turning yellow and falling off.
If some of the stems have lost leaves, it makes me wonder if the plant is being rotated occasionally so that all sides of the plant receive bright light from the window. Depending on the type of potting medium being used, if it's a soil moisture issue, the problem may very well be originating at root level.
Hopefully others who grow Hoya bella will recognize the issue you are having with this particular Hoya and be able to offer suggestions on how to correct it.