[Scip] Problem with debug solution

[Alexander Schnell]

Dear SCIP team,

I implemented a constraint handler and there seems 
to be a problem:

With a certain parameter setting, SCIP tells me that an instance is
infeasible, whereas I know that there must be an optimal solution for
that instance. SCIP detects the infeasibility during presolving. 
If I switch off presolving, SCIP finds the optimal solution. 

When I try to run SCIP with a debug solution (#define
SCIP_DEBUG_SOLUTION ... in debug.h), it is read
but SCIP does not print out any violation detected for the debug
solution. Is this because the infeasibility was detected during
presolving?

Do you have an advice for the debugging of such situations, i.e. 
a wrong infeasibility detection during presolving?

Thank you in advance.

Best regards,
Alexander Schnell