Got the same issue with Donkey Kong Country, had to increase sync Vth to 225. Though it doesn’t happen the first time I watch the intro, only on subsequent runs. I think it’s not the explosion, but that roll-up effect of the title screen that follows it, which is not used the first time. But at least DKC resyncs after 2-3 seconds, unlike Yoshi’s Island, probably because the intro scene there is minutes long, causing more problems at some point.
My SNES is an unmodified PAL model.
Now I’m curious how much of a difference the shielded luma cable I ordered will make once it arrives, if any. If only a PACKAPUNCH cable fixes this I might have to upgrade once more^^”