It sounds to me like you may be running into a bug or some sort of network issue. I would create a support case so you technicians can take a look.
I'm in a similar boat and wondering if you ever found a solution to this limitation.
It's 2019 now. Any solution on this problem? We have around 22-31 dashboard need to be constantly signed in and display the information with periodically refreshed for 15 minutes.
but after a day we start to have few dashboard are at login screen.