Hi Arlene,
I suspect this is script related. I’d take a look at the logs first and see if there are any scripting related errors. I’d also compare the scripts in QA/Prod and Dev/Sandbox to see what is different.
Another thing you could try is to turn off all the scripts. Manually populate the extension fields on the Agreement and see if you are able to reproduce the problem. At least this will tell if the problem is with the scripts.
Hope this helps.
Regards,
Vikram