I was noticing that too. I find if I can match 5 and get a pearl, then swap with the gold tokens it turns them all to gold squares. I've ben trying to get two pearls to swap to see what would happen. The key has to be swapping special gems because that's wjen my score is highest.

I also matched a pearl with a star. When I did it low on the board it didn't work. But when done closer to center it did.

I've dropped plenty but I always have two left. The trick is to get a silver pearl and a directional gem on the bottom to swap. Often this gets 2 symbols to drop If the shield is already removed.