These trains were locking up for arbitrary reasons after being serviced at third-party workshops. The manufacturer argued that this was because of malpractice by these workshops, and that they should be serviced by them instead of third parties.
We found that the PLC code actually contained logic that would lock up the train with bogus error codes after some date, or if the train wasn't running for a given time. One version of the controller actually contained GPS coordinates to contain the behaviour to third party workshops.It was also possible to unlock the trains by pressing a key combination in the cabin controls. None of this was documented.
After those findings were made public the former Minister of Digital Affairs Janusz Cieszyński confirmed the Polish government had known since May.