Well, i have two saved non-default (non-empty) models (#1 and #2). When i open and then close models repeatedly (#1-#2-#1-#2...) pgm is crashed. Stack trace in the mail. In tab 'loaded model' - default empty model. This is strange, because i don`t load it.
in the mail
I cannot reproduce the crash using the steps you reported. Maybe you did some other operations before close the models.