E143 error connection to primary decoder every evening before 7 pm

I have had a DSTV approved installer upgrade my system to have 3 decoders connected and this worked perfectly for about 4 weeks. For the last 2 weeks we get the e143 error every single evening just before 7 pm and the next day all works perfectly again. I have phoned the call centre several times and walked through the endless unplugging of cables and resetting of settings with no luck. My installer has come to check the system 3 times and can find no fault. We pay more than R1000 per month and we are not getting the service that we expect. What can we do to solve this issue as I believe it must be a dstv issue when all other things have been checked and that it worked before and now only works during the day . I hope I get a response from dstv as I cannot get to speak to anyone other than the call centre when I call.