Always look for a more efficient model. Bounds could be tightened; coefficients’ magnitude can be reduced by rescaling of the data; you might not need certain constraints or logical conditions when using a different approach. Sometimes, just a different formulation can help, for example, a logical condition can be manually linearized. See sections Efficiency considerations and Numerical accuracy.

Play with AMPL options and Solver options. Prominent ones are AMPL presolve (switch off: ampl: option presolve 0;) and solver’s presolve (ampl: option gurobi_options 'presolve=0';) and others (tolerances, numfocus, intfocus, etc.)

To see what MP and/or the solver do with your model, export the solver’s received model, and, if possible, the solver’s presolved model:

option gurobi_options 'writeprob=disj.lp writepresolved=disj_pre.lp';
option gurobi_auxfiles rc;     ## To use var/con names

MP offers ways to explore automatic reformulations.

If you decide to contact AMPL or solver support, please provide a (possibly reduced) version of your model reproducing the issue. Please also provide the AMPL solver version by running highs -v or solver logs obtained with options version outlev=1. If you cannot reduce the model and don’t want to show it, give us just the NL file produced by

option auxfiles ''; write bdisj;

For solver support, use MPS or another full-precision model format.