Unable to find site of GI bleed with CT scan

My dad has had internal bleeding from his small intestine since November, and just had a double balloon enteroscopy that his GI doc thought would be able to fix it. Unfortunately the scope wasn’t able to get to the site of the bleed, so they sent him to get a CT scan which also did not find an active bleed site. What would be the next step to find the site to be able to stop the bleeding? He has to continually get blood transfusions so he is still losing blood somewhere.
I’m trying to figure out what questions to ask the medical team to make some progress. Thank you