What do you think?

1)  They tell you their only income is Social Security. 

2)  Then they tell you they have rental income. 

Maybe a few neurons short of a synapse?  Be careful around people with early dementia, their kids may sue you if you overlook their condition. 

Do they still have copies of their 2017 return?  Or maybe they forgot where they put it.  Previous preparer still around?  Or maybe an injunction from the government, banning him from practice.  

Good luck.