In the image below, all three droppers started with 32 redstone blocks inside, and each one is hooked up to the same comparator clock. However, the one connected to the redstone dust from the direct output of the comparator only activated once before stopping even though the comparator clock is still running. It will drop another single item if disconnected entirely and reconnected but the issue remains.

This is not the case for the other droppers connected to different parts of the redstone line. As you can see all the redstone blocks were quickly ejected.