@mxc0bbn … I have seen something close, but not quite the same. (See Issue Setting Relay for a Linux Client on Initial Installation). In my case, I defined the relay in besclient.config by IP address, not by hostname (thereby negating any need for IP hostname resolution). After that, I had no problems, even between system restarts. Maybe give that a try in your situation.
Of course, that means that when I look at the BigFix console, I might see the same relay twice - once for those clients who connected to it by IP hostname and once for clients who connected to it by IP address … but I can live with that.
–Mark