In Gurobi 9.1.0, there is an issue with the handling of pre-specified user cuts that are >= inequalities.
These inequalities are mistakenly treated as <= inequalities, which can lead to wrong answers.
This issue will be fixed in the next technical release.
Workaround: Specify the cuts as <= inequalities by multiplying the constraint by -1.
Note: A pre-specified user cut is a constraint that has the attribute setting Lazy=-1.