@qrumba

Have you checked that the MS flag (MapSource flag) is 0 in the IMG-file?
Files created with MapSource / MapInstall will get MS flag = 1. BaseCamp needs MS flag = 0 when reading memory card IMG files.

Example with MS flag = 1
Code:
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Check the IMG-file with gMapTool. If MS=1 then change that with gMapTool. Enable "☑ Advanced options" and then use "Write" tab and "☑ Set version in header" -> "MS 0".