I discovered this thread during a search because my brand new SD200 has the same issue as the OP describes. I also use a Stridsberg multicoupler which feeds three scanners, the SD200 and a pair of BCT15X radios. The 15X scanners have perfect audio on the same frequencies that the SD200 has serious crackling noises for strong signals (VHF/UHF NFM).
So I removed the multicoupler and connected the SD200 directly the the single coax coming from the antenna and seems the crackling has gone away, at least on one frequency. As per the Stridsberg specs, the coupler I have produces 2db gain. So, for example, if I receive a signal 2db stronger than the frequency I am listening to, it would seem logical that the crackling would manifest again?
Likewise, it would also be logical that I will not receive signals that my trusty 15X's will receive which would have a 2db advantage.