I've had unit disbandment happen in the last several versions. It only seems to trigger if you have BOTH negative
per turn AND zero
in your coffers, and it seems like it is more likely to occur the more units you currently have. I figured this was because the random % chance is rolled per unit and the % is quite low. The only time I run into gold issues is during the Ancient era when I'm trying to be a warmonger, so I have never really triggered the flags for enabling random unit disbandment in the later stages of the game.