With the blocks arranged like in the pictures, whether its a dropper or a dispenser, it will trigger on redstone signal the first time or two but stop working after that. Breaking and replacing the redstone on top will allow it to be triggered again.
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Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases. If this has been done, we can reopen the issue.
Keep in mind that the "Resolved"-Status on this ticket just means "Answered", and that we are waiting for further information on whether this issue still exists or not. We will reopen it as soon as the requested information has been delivered.

Ticket resolved as incomplete, because no answer in a reasonable amount of time (1+ year), if it still happens, please update the ticket.

Must have missed the first comment. Bug still exists in 1.11.2 and 17w06a.