I play synchro shien with this. Synchro shien negate a trap and after that opponent play another trap. Great shogun allows play only one spell or trap? Am i wrong?
It's not bugged, you negated the ACTIVATION of your opponent's S/T with the synchro, so it's as if your opponent has not activated any this turn. As a result, your opponent can activate another one.
I don't agree with people saying that because it was negated they can still use a second spell. They still activated it and even though it was negated it was still activated. This is just a case of sloppy coding that makes it a shame as it's pointless using them together.