Strange behavior i must say and i must also agree that it looks like epg is effecting this some how, Usual EPG works like crapp for IPTV Streams so next question must be
how do you assign your epg to the Streams?
And how do you build your bouqets?
for example it could be YouTube liveTV and I added epg from sat channel using option <map to dvb service>
at first, of course, I added livetv stream to buquet