In ME23N, material data tab, PRODUCTTYPE is set to 1. How can we remove that 1?

[eliza4c]

We believe this is the cause the GR checkmark is getting enabled under the "Delivery" tab when we click on "Final Invoice" under the Invoice tab which in turn is causing the error: 

Indicator for GR used not allowed
Message no. MEPO023

The notes that suggest that this is an issue in SPRO or OME9 where the GR binding is checked is not helping as that is not our case. In fact, we've had this same config since we were in R/3 and this was never an issue. This happens sporadically for some POs but not all and the only thing we see in common for the ones having the issue is PRODUCT TYPE = 1 under material data tab. Please see screenshots attached.

Any suggestions on how to fix this would be greatly appreciated. Thanks!

 

Elizabeth