You're right. We had the right idea before but we got confused about this issue. I changed all the XT1121s to XT1111 and vice versa. We already know which channels are sourcing and which not. Updated the wiring spreadsheet. The chassis seems to work. It's time to pass it over to Chub.
I don't think this is an accurate statement. XT1111 modules have sinking digital outputs, while XT1121 modules have sourcing digital outputs. Depending on the requirement, the appropriate units should be used. I believe the XT1111 is the appropriate choice for most of our circuits.
For digital outputs, one should XT1121. XT1111 should be used for digital inputs.