Friluftskartan Prime regions shares the TDB file that is used for more than one region. Family 1758 may have img map tiles from "00000002.img" to "00000013.img". It's only the ""00000005.img" file that's used for region 13L.

Try to create copies of "00000005.img" in the FAM_1758 directory and name them "00000002.img" - "00000004.img" & "00000006.img" - "00000013.img". Then run MapConverter that should finish without errors since it finds all img-files from 02 to 13.
Erase the source and destination data for the redundant copies of "00000002.img" - "00000004.img" & "00000006.img" - "00000013.img".