Hello @TomS
They finally worked, but we had to run "service unsupported-transceiver" as you said. Cisco wanted to scare us with this message after that.
"Warning: When Cisco determines that a fault or defect can be traced to the use of third-party transceivers installed by a customer or reseller,then, at Cisco's discretion, Cisco may withhold support under warranty or a Cisco support program. In the course of providing support for a Cisco networking product Cisco may require that the end user install Cisco transceivers if Cisco determines that removing third-party parts will assist Cisco in diagnosing the cause of a support issue."
While digging in Cisco forum we found this.
Q. Do the Cisco Switches interoperate with SFPs from other vendors?
A. Yes, starting from 12.2(25)SE release, the user has the option via CLI to turn on the support for 3rd party SFPs. However, the Cisco TAC will not support such 3rd party SFPs. In the event of any link error involving such 3rd party SFPs the customer will have to replace 3rd party SFPs with Cisco SFPs before any troubleshooting can be done by TAC.