inIn the function description they specify that this function is for recordings from Wildlife acoustics song meter recorder. Maybe this could be somehow at the origin of the issue? something with the name of the recordings maybe? they use in the function the argument rmoffset=TRUErmoffset=TRUE
that is really important for SM4 recordings. I would try with rmoffset=FALSErmoffset=FALSE
and see if that solve your issue. I could look more into it but I would need your files to play with the error.