I have this idea developing still, and I might write it, but for now, here are literal bits and pieces of it.
During the Bruce-In-The-Timestream incident, Jason was actually on a mission with the Outlaws and came back shortly after Tim and Bruce did.
He was rather pissed after getting everything from Tim and Cass, and Bruce, then Damian, then everyone.
(Yes, he gave Damian a talk-to.)
He was most pissed at Dick. Yes, he knew his brother wasn't in the best mental space, but that didn't excuse what happened with Tim. Especially since Tim (in this AU at least) didn't even tell anyone besides Bruce, Jason, and Cass what really happened. Also, Alfred found out because Alfred knows all.
Yes, only they know about the missing spleen. And the other things.
So for a while, Jason kept quiet, though Tim was avoiding Dick and Damian, was hanging around Jason more. Both of the D's were a liiiiittle jealous of that. Dick didn't like that Tim seemed to feel safer around Jay 'all of a sudden'. He knew it was his fault, but still.
Damian was just Confused with a capital C. Jason talked to him, though, and laid it out, but told him to give Tim some space first.
Jason can tell that the two don't like that Tim is avoiding him and hanging out with him. But right now his attitude is 'DICK SHUT UP THEY'RE MY LITTLE BROTHERS TOO.'
Bruce knew everything but didn't know what to do. Alfred told him to 'let the boys sort it out themselves.'
Eventually, Dick finally got Jason alone in the cave, and it rose to an argument. A big one.
They stopped talking to each other for a while after that.
I haven't decided what happens from here other than after a while they do talk it out and all.