I found the reason why at a customer:
2020-10-06 18:06:15 /THREAD(2) TreatThisSocked blocking socket 5 with use 3
2020-10-06 18:06:15 LGR looking for: 4 63748
2020-10-06 18:06:15 LGR in index: 1:SHVc:PSERNR
2020-10-06 18:06:15 LGR D4IndexDelete found no record
2020-10-06 18:06:15 LGR dump of call stack
2020-10-06 18:06:15 LGR D4IndexDelete found no record, now dumping index:
Afterwards you get wrong decimals in the system and you have to restart.