I'm not sure this is the appropriate place to post this. If you deem that it isn't, I hope you can move it to the appropriate place. This problem first appeared to be a Gallery/Server problem, but later revealed to be bigger.
I have this simple workflow that worked perfectly in Designer:

When I went to publish it to server, I received the error:

Interestingly, when scheduling the workflow, it still completed successfully, in spite of the log entry which shows the same error. But the results appeared in the output table as expected.
When executing the workflow from the gallery, the same error appears, but again, the results appeared in the output table as expected.

Until this point, the problem appeared to be entirely Alteryx Server related. However, when I added an Event in Designer to send an email on run with errors, Designer still completed, showing no errors.

But I received an email with the same error:
...
Started running E:\ProgramData\Alteryx\Engine\Staging\977eb6df-ca95-4695-a2b5-f14e81cc8bdb\New Addresses - Geocode and append.yxmd at Wed Jul 12 15:00:17 2017
00:00:0.156 - Error - ToolId 228: Macro Input cannot be used as a question input for this action type.
...
So, I opened the US Geocoder macro and searched for tool 228. That tool is a simple Select tool which has no direct connection to any type of interface tool. This error doesn't make any sense to me. Is there a bug in the US Geocoder or not?
Can anyone reproduce this problem? Any help would be greatly appreciated. Thank you for your help!