This bug is best and easily explained through pictures, I suggest you take a look at the four pictures at the bottom.

This bug is a bit harder to explain through text, but I'll try my best. If you're directly powering a block, which indirectly powers a repeater, through a powered redstone cross then turn that redstone cross into a redstone dot, then the repeater will unpower itself. No problems there. Then, if you attach another redstone component (such as a repeater or a redstone dust) to the redstone dot on the side opposite the indirectly powered block, then the redstone dot will turn into a redstone line, but it will not update the directly powered block and thus the indirectly powered repeater will remain powered off, even though visually and using block-states the indirectly powered repeater should be powered.

That was a complicated wall of text. What I'm trying to say is, the redstone dot being changed to a redstone line from another component isn't updating properly.

It's really hard to explain through text, so just take a look at the four pictures below.

Step 1:

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Step 3:

Step 4: