During 1992 when N O W Comics (Ghostbusters Firehouse) were in their “now better than ever” phase, they began a new run with some new stories for their The Real Ghostbusters title. This could be a blanket statement, outside of the comics their was very little to support Ghostbusters. The hit series had ended a 7 season run a year earlier, Kenner had ended making The Real Ghostbusters toys, and Ghostbusters II™ had come and gone from theaters, at least to people’s homes.
Whether any of that played a factor in Now’s decision to end the RGB comics run I don’t know. They had been looking ahead from the Tobin and the Maze of Time story arc that had been prevalent during volume 2. The next comic, issue 5, originally scheduled a month earlier would have featured an interesting story about a ghost who for whatever reason hangs around the Pentagon and of course threatens the survival of the human race. Or at least it would if The Real Ghostbusters probably couldn’t have “zapped and trapped” in time.
I don’t know how much of issue 5 Barry Petersen, Neil Grahame, and Jim Brozman completed. It wouldn’t surprise me if the script/story is on-line. Checking out the cover, it seems to have a Ghostbusters II influence.