Hi, @chriddyp! Thanks so much for looking into this. It was funny, because as I was typing this response to you, I was able to figure it out. 
Here was the issue: Since I was taking dashboards from my coworkers, I was incorporating them as is into the server I made to handle multiple dashboards (using the great example you gave here, actually).
Exceptâand Iâm âfacepalmingâ nowâof course each of those individual dashboards were set up to run independently with their own servers before being sent to me. I needed to incorporate them into the app.py file from that multiple dashboards example, and eliminate the oldapp references in the individual dashboard files. Doh!
I hope this rather silly revelation makes sense. 