Could be a power supply problem. See comments here:
http://www.howtomendit.com/answers.php?id=303877
http://www.amazon.co.uk/TVonics-DTR-Z250-replacement-supply-adaptor/dp/B008RCBJCQ
Surprised you didn't come across comments like that already. You DID try a search for solutions yourself, didn't you?
XXX
April 2016