2099231 - Language "Not Imported Completely" in SMLT

Upon installing a language package via transaction SMLT on your system, you noticed message "Not Imported Completely" on the right side of the language name, similar to the below screenshot:

Another example:

If you click on the yellow triangle besides the message, you'll get the following information:

If you check the import logs, as well as the corresponding job's import logs, you notice all of them finished successfully:

 and

 There are doubts whether the language was really imported correctly or not.

RSTLAN_IMPORT, import, feedback, imported, postprocessing, necessary, upgrade, completed, message, number, no., PU139, "S 240", version, 731.F.15, STRALAN_MSAG190 , KBA , BC-CTS-LAN , Language Transport Tools (application server ABAP) , Problem