THat is the software that causes the problem. I use Total Recorder or Audicity to do the actuall recording (Though I don't so much use TR any more)
THe software works by listening for SILENCE. sadly old cassette tapes do not have a lot of SILENCE. on some programs you can adjust the SILENCE thresholds but even then it does not work well because some musical pieces have short dramatic silent parts and that will trip the track counter.
WIth Audicity or TR and the "Audio scope" you can very easily edit. Does not take long at all. And yes I've done that job .
The version of Total Recorder I used to use was the Professional version... My Daughter is a rather good Classical Flutist and music teacher. Very well trained by some of the world's best including Ervin Monroe late of the Detroit Symphony. also Jeff Zook and the Late Phil Dykeman of same. Jeanne Baxtresser of teh NY Philharmonic and others.
While she lived in Detroit... I was her recording engineer recording all her performances or class concerts.. I've got soem GREAT recordings of Wayne State University Wind Symphony .