This should not be new. The sourcemaps are indeed not parseable and it can make sense to show this warning, although I don’t see it on my end.
That said, it should be nothing more than a warning and has no impact whatsoever on what you’re doing. In a nutshell sourcemaps are debugging tools aimed at the sketchfab team.
I would suggest looking for an alternative explanation as to why no data shows up. A new viewer api version has just been released (as you mentioned) ; maybe a bug has been introduced. Could you give more details about what you’re doing ? e.g. code snippet