Router getting cut off

When my roommate tries to coect to the wifi from his room, the router cut off. I think the problem is only when a device is in his room. We are having no issues while using the inteet in the hall or in my room. He used to coect to wifi from his room before. What could be the reason for this? The router is Smart RG SR360n by our inteet service provider Acanac. The coection is DSL. I would like to get some suggestions?

Thanks for reading