Branching on t_x21 led to this error
[scip_branch.c:1061] ERROR: cannot branch on variable <t_x21> with fixed domain [-0,0]
So, my guess as to why this did not work is that during presolving, SCIP fixed this variable to be 0 and hence it throws an error if we try to branch on it? Is this correct? (Also, this error occured after a restart)
Yeah, branching on a fixed variable does not make much sense. You should check the bounds before selecting a variable as a branching candidate, I suppose.