Peculiar boot behaviour in Unity

As of last week my game is only booting intermittently. On my first attempt this morning, it just hung with the three dots and never reached the Unity splash screen. I cancelled the program after about 3 minutes. Then I ran it again and it booted in a few seconds. This behaviour started at the end of last week when two things happened at more or less the same time. Firstly I added the entitlement check code. And secondly, there was a system update.

Note: I was not connected to Wifi during these tests.