Hi RSK,
When the fields are unselected for Fields only in known exit, Then colleague may not be enhanced these fields. Just he added to extract structure and didn't maintained CMOD also.
Go SE38 - ZXRSAU01, Find(CTRL+F) - 2LIS_17_I3OPER.
if you won't find that data source name, you may need to look at BAPI part enhancement.
As my guess, code may not be maintained so you are not getting data for added fields.
For LO data source enhancement :
There is no anything issue. CMOD code may not be maintained. your colleague may left this project in middle of this work.
So maintain code at CMOD and try to check it later. Selection for Field known in exit only. keep it. there is issue with that. for enhanced fields always need to select.
Thanks