Logs for a file named ABCDEF.flac showed up as
2022-01-19T16:31:55 [ERROR]: SndFileSource: could not seek to sample 90059776 within BCDEF.flac (No Error.)
So, evidently, there is no need for the substr(1).
_name is a PBD::Property<string> which already uses .val() for <<.
The same pattern is found and fixed in sndfilesource.cc and
coreaudiosource.cc .