When you record a tape on both sides using DCC-Studio, the tape will keep recording for few seconds before it actually switches sides. I don’t know if this is what you’re seeing and you’re just not patient enough (sorry I’m not trying to insult you), or if something stops working for some reason right when it’s supposed to do something. If you know what I mean.
When you make a recording with a DCC recorder, and the recorder decides to change to side B, it actually writes a short marker on side A to remember that it did that. The idea is that in most cases you want to switch to side B as fast as possible because time goes on. At a later point in time, a recorder that plays the end of side A may decide to make the marker longer but I don’t know if any recorder does that.
When using DCC-Studio, you’re not recording in “real-time” so it doesn’t matter if it take a while. So the program writes the reverse marker that you would normally write at a later time when you use the Edit feature of a recorder. If the program writes a “Go To Start of track B” marker (does it do that? All of a sudden I’m not sure), it has to write the marker, fast forward to the end of side A, reverse, record silence for a little while to skip the lead-in tape, and then start recording again. All the while it will display the “Reversing Tape” message.
I suspect in your case the computer may send the reverse command to the recorder, and then something unexpected happens on the recorder that confuses DCC-Studio. The recorder sends an error code back to the program that the program doesn’t handle correctly, and the recorder thinks it’s done while the program is still waiting for the recorder. Perhaps the tape is the exact right length for your recording, and the recorder detects the tape end at the same time as DCC-studio decides to reverse the tape. The recorder reverses the tape because it detects the tape end, and then it gets a command from the computer to reverse the tape again. It sends an error code back to the program but the program ignored the error code.
This is all speculation but I figure this is one way that something like this could happen. You could verify this by making the last song on side A in your compilation a few seconds shorter, and then trying to re-record it. See if it makes a difference. Tip: If you’re recording a compilation, you could copy the compilation file (with File Save As) and delete all but the last track on side A. Then wind the tape to the end of track A and record the compilation starting at the previous tape marker. I wonder what happens.