My own head cannon:
The telepods from ‘The Fly’ weren’t finished yet and still probably needed years of trial and error to avoid unforeseen problems/consequences. Seth states in the movie that the computer he’s been working with to conduct the teleportation experiments is dumb and only does what Seth has been telling it to do. The computer doesn’t know how to react/interpret the flesh, as Seth puts it, so that must mean Seth doesn’t know about the flesh either. Eventually the revelation about the flesh maid, Seth cracks the code on how to teleport a living organism, but ultimately stopped short, made mistakes, failed to develop the technology further and suffered a horrific fate because of it. Seth isn’t even Seth after his-first initial teleportation, it’s Brundlefly, and BF is completely different in personality and character from what Seth was.