I started using HA only about 2 mo. ago, and therefore had to add a huge number of devices in the first couple of days and even some weeks later (as I bought more than half a dozen of Zigbee sockets afterwards), so I had this issue frequently. I basically discovered a similar work-around – for me, often “force-reloading” the dashboard did the trick (“Shift-Reload” in the browser).
It’s obvious for me that there must be some “quirk” inside HA that sometimes prevents proper setup of newly added devices.
(This is only one of several annoyances I have with HA so far… I would love to help solve or at least further investigate this if I knew how to do it…)
(I hope this doesn’t get across as not being thankful for what we get for free…)