i was just restarting play mode when it failed to produce chain on the first try, this was the same when generating in edit mode [clear&generate button]
when it failed the displayed chain was very short: 1- 3 rooms max - this seems to be correct though since there _are_ rooms w one entrance/exit only and requested minimum was 5
(as a sidenote: the condition for picking the next room should be probably more advanced and not entirely random if room template with more exits exists and end (edit: minimum rooms) was not reached - to not run in these premature dead ends; - but moreover there's no guarantee that the generation has successfully finished currently - I think you're safe to loop/yield until it is instead of hard limit though :-), but note that I'm totally fine with current state and can check result in user code if necessary)
'400' is enough for everybody, until a kitten is burnt ^_^
Cheers!