They probably are not in gracenote.
So question. The stations missing EPG, are they important. If not just block the stations so u do see them.
If they are important try other epg service till u find one that has them.
I have one source where gracenote only has about 2/3 of my station
So I made a custom m3u (m3u4u is free. I dont use them) that contained those stations. Then made a different m3u that contained the non working stations and used my paid epg service. Which got me most of the missing stations. The ones I couldn't find I just blocked.
When dealing with custom stations (m3u, iptv etc) epg data is hit or miss. There's not much I think the devs can do about that sadly