Microflow in Acceptance = Microflow in Production
Data in Acceptance != data in Production
If the code is working on Acceptance and working with the data present there, the only difference is the data (volume). Do you experience memory problems on the server/node? If you are doing a lot of logic in the Microflow creating the list, try migrating the Microflow to a Nanoflow.
Check and see if the security on the associations is correct. I think I read a post on this somewhere on Google or even in Mendix forum. The jist of it if I remember was that once you turn production security on, you also need to make sure the security for associations between the entities are properly configured, or you will indeed not see data.
Don’t know if this is helpful, but what you’re observing could be related.
Are you able to take a copy of the production database and backsync it to a local environment so you can single step through yourself?
It feels like there isn’t an object being passed and if you have a local copy you can test this for yourself.