picture keeps dropping

have new visio 4k tv and ordered new gemini to go with my genie 54 to get 4k for new tv.  problem picture goes blank, shows visio logo, then comes back in about 12 secounds. tech from dt has ben out 2 times finally replaced new gemini with another one but picture dropped once after tech left. he said the gemini are crap and they have alot of problems with them, last time pic dropped the tv said check connection to tv , so should i get new hdmi cables? its really frustrating signal comes from sat to genie then to gemini then to tv!