QCQP model doomed infeasible in presolve, however it is not

Hi Jonas,

and if you want to try something on your side while waiting for us to look into the issue in presolve: We do have the refinops functionality https://www.fico.com/fico-xpress-optimization/docs/latest/solver/optimizer/HTML/REFINEOPS.html which is meant for this usecase of optimizing a mixed-integer problem, fixing integer variables, and then reoptimizing. Of course it cannot predict the quadratics that you would add for the second solve, but if the problem is caused by some of the linear constraints becoming slightly infeasible after performing your fixings (where there can be slight differences with regards to the tolerances used by the LP solver and in presolve), then this might help. You can either set the ninth bit (so set REFINEOPS to 17 + 2^9 = 531) if you want the initial branch-and-bound search to completely reject solutions that would become infeasible after fixing the integers and resolving the problem from scratch as an LP, or you can set the tenth bit (so set it to 1041) if you want it to attempt to clean up the solution, but not reject solutions outright due to this.