This is one of the most discussed least resolved issues in the comments. All I have to say is I have done a lot of playthroughs and never had a problem getting the clash, and I mean the first or second time I entered the bar after I met the requirements. I have never let bandit's morale drop below 80. Maybe try raising morale, I really think it increases the odds of it happening. And for sure check what the thug is doing if you didn't already. I don't think it matters when you do it (that would be a hell of a "lockout" to write in) but I seem to remember at least one playthrough where it triggered soon as I did that.
OK hope your are saving so you can go back if this don't work.
Has the thug ever shown up? You said you were caught up with all of Jester's tasks, right? And talked to Harold about the bandits? And Bernie and Logan? I would try to go all the way to 100 and check for the thug in a couple days. And do it before Night (20:00) to see if that works.
I know I have seen him in the tavern early as 14:00 when it opens, and I am pretty confident I got the clash once at 19:00. I know Night is 20:00 but the alternative is Daylight, evening is vaguer, it is 18:00 or 19:00 for some events.
Anyway I save and reload all the time checking things, may not be the way you want to play. That is all I can think of to try and help.
Talk to Bernie, there's one time in his talk menu and then there is a one time choice in his top menu "Talk, Trade, Additional Job, Nothing right now". It's something like "Supplies for camp".
Here's my best recall, you take the task, go see Bernie, talk to him, go back to Jester, end the task, go back to Bernie and choose the Top menu choice, go back to Jester and talk to him about it.
I might got that reversed, but you get the idea. Jester->Task->Bernie->Talk or Choose->Jester->End Task->Bernie->Choose or Talk->Jester->Talk.