I don't know why, guessing it's a header problem, but when I cut the show into smaller bits to save as a .wav instead of .w64, then split in cd wav, saved using "alternative 24 bit options" Frontend seems to work fine.
One odd thing, Frontend is saying:
Encoded by FLAC v1.1.2a with FLAC Frontend v1.7.1 FLAC tag written
What's that?