Some FLAC albums won't play on LMS

Out of my over 10k albums indexed on LMS, there are a few that won't play on LMS. When I try to play them, it would display an error message saying "Can't open file for...". The files themselves seem pretty normal. They're 16/44 files, with metadata displayed perfectly on LMS, and play fine directly on my computer on my phone, but won't play via LMS to Squeezelite or to the computer or phone via LMS DLNA plugin. I tried rescanning the whole library and it does not seem to be an indexing issue. I normally set LMS to transcode flac to wav (for a slight SQ benefit), but when I set it to play flac natively, the files would play. I can't see why these particular files can't be transcoded.

Any idea what could be causing that?

Thanks.