Like what kind of problems?
Here has been discussion in another comments about overusing ARs for trying to achieve too complicated things that'll lead to DB performance problems. As stated elsewhere here, AR is good for CRUD operations but after that you should use Query Builder or plain SQL to achieve the more complicated cases.
As an interesting side note: Laravel's AR ORM (=Eloquent) is built on top of the Query Builder so you can leverage Query Builder with AR if you know what you're doing. Can also lead to big problems if you don't realize the possibilities and the caveats.