Error code 20000 when using user cuts

When adding user cuts via a callback to Gurobi, you should disable certain dual reductions during the presolving phase. This is to ensure that the cuts can be transformed to the presolved model. 

Please set the parameter PreCrush to 1 to enforce this when working with user cuts.

Otherwise, you might encounter errors, typically error code 20000.

Further information

• What is the difference between user cuts and lazy constraints?