Those logs look fine, ie. the files are being opened and detected as FLAC by BASSFLAC.
tongub, can you please confirm how you are creating streams of different file formats? It looks like you are using the add-on specific functions (eg. BASS_FLAC_StreamCreateFile), rather than loading the add-ons via BASS_PluginLoad and just using BASS_StreamCreateFile? If so, do you try all of the add-on specific functions, or do you choose one based on the file extension? If the later, perhaps the problem is the "FL~" extension mentioned above, ie. it isn't being treated as a FLAC file?
I would recommend simply switching to the BASS_PluginLoad method