To those that may come across this thread, I cannot explain why the issue is occurring, but if you pass a name to the default data when utilizing 'adddata', the legend will look normal again. Fixed
#Don't use this:
cerebro.adddata(data)
#Use a name with the data:
cerebro.adddata(data, name='OHLCV_jt')
The name comes across in the heading / legend of the master Bokeh plot as so:
snapshot1.PNG