It does have the white possibly toxic "milk" when u cut branches I'm pretty sure it's an African milk plant I wear gloves when cutting branches..we're those pics Good enough?

too little sunlight/heat and too much water maybe... rotting trunk. may need to chop off all upper section and reroot to save plant.

Cut until you're in obviously healthy tissue, making the last cut with a clean knife. Have a bucket of lukewarm water nearby and wear appropriate PPE. The water's for staunching the flow of latex, the PPE's to protect you from chemical burns. Cut a healthy segment and stick the dripping end into the water for a minute, then set aside on some newspaper to dry and stop flowing. Wait a week, then dab the ends in Rootone, wedge slightly into soil (one that's at least half-porous material) and prop up with rocks/pots/stakes, Put in a sunny location and don't water them. Mist the stems every few days. You'll likely see growth (and therefore roots underneath the soil) in two months. It'd be good if the atmosphere was warm (ideal would be a heat mat for the night).