Hello Peter, Frank,
However, I would not expect numbers _that_ wrong in this case. However, I would like to know if this should indeed be the problem.
Are you running with Carpet's poison parameters turned on (I always advertise to do so)? If so, then you are likely seeing poison. Most likely caused by bad data on past timelevels (caused by eg computing the to be integrated quantities only every so often and not on every iteration).
Yours, Roland