I found this issue in creative mode.

I built a structure with command blocks like this

It shows that when I have more than 3 slime balls, it will give me a tnt and remove three slime balls, otherwise it will show me the failed message.

Normally it should work like this:

But when I set a tickingarea (I used the sculk to mark it)

It worked like this:

So, the priority of blocks in tickingarea may higher than redstone transference. But it shouldn't like this, and I consider it as a bug.