Did you try out another EPG source and see if the problem occurs?
Also check your private message in the left upper corner (messenger logo) called conversations. I texted you.
Hey i am using Nvidia Shield TV too..
SipTV is good but i tryed all the apps even KODI, i was happy with Perfect Player.
I'd suggest, try Perfect Player, more options and a friendly UI.
Options like: Start on boot etc is handy for IPTV