I have my router downstairs and a Apple TV upstairs and no problems streaming.
I have my router on a table right next to my living room TV with a Chromecast about 2 feet apart.
They both can have issues with streaming no matter the distance if my wifi speed gets screwy which it does on occasion.
I'm not certain but a new router could be a issue.
My sister had a issue where her Galaxy S3 wouldn't wouldn't automatically connect to her home wifi if she left and returned home but it would connect to my network faithfully when she would visit leave and come back.She got a new router problem solved.