JKD_666 OK, that's good to know. Almost every instance of the PartySwitch bug has been correlated with starting a new game around the time, or shortly before, you go into the Prison. The code was bugged so that in some cases save data from previous or subsequent playthroughs leaks into the saves of other playthroughs. You're just the first person who has seen the effect happen to the Incubus Prison party as opposed to the "default party". Probably because you're the first person who was affected by a new game started after 0.59.3.
The concern was that if you had not only not started a new game, but NEVER played a previous one, than the completed Incubus Prison save data had to be coming from somewhere other than your TLS save data, and the only sane explanation would be that the data was somehow being loaded into the installation, which raises all sorts of questions.
I do have the fix for your version of the bug coded, and I intend to pass it on to Sierra this weekend after some more bug squishing. (Need to check the level of prison Simon though.) Not sure if it will warrant a 0.60.4 release or if the fix will come out with 0.61, but I'll be posting a patched version here for testing.