Early on in my use of the Red Series Switch I had a very similar issue that I was able to isolate to happen when the dumb switch was only in a certain position. The intermittent behavior was fixed using some different LED bulbs around the house.
@Eric_Inovelli has comment in another thread about the fact that some dimmable bulbs causing issues with the Red Switch detecting the dumb and Aux switch types. In my case I was not using dimmable bulbs, but the issue did go away…