Hi @Deyco ,
By my research, it is recommended that you can try to use below command line(run as administrators) to install cumulative update 12 for your Exchange server 2019. Reference: Upgrade Exchange to the latest Cumulative Update | Microsoft Learn
<Virtual DVD drive letter>:\Setup.exe /IAcceptExchangeServerLicenseTerms_DiagnosticDataON /Mode:Upgrade
If there is any error message, please don’t be hesitated to provide it to us (please be careful to erase private information).
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