Hello,
The issue was not only with KPN but was rather related to the transmitters used for the n28 band in the 5G spectrum. The modem update seems to have addressed the issue, as users who have updated the modem do not report any further issues.
As for imposing IMEI restrictions, that should not be the case, as RUTX50 is certified to work in the entire EU.
However, it should be kept in mind, that RUTX50 is only intended for the European market and will not work in the US.
Best regards,
DaumantasG