Tvheadend

Post example of your EPG content.
EPG is sorted by time.

EPG data is supplied by EPG Grabber Modules, listed in Config -> Channel/EPG -> EPG Grabber Modules. Each one has a priority, and the EPG for a channel is taken from the module with the highest priority which has some data. There is no attempt to 'merge' sources, and a higher priority source will be chosen over a lower priority one even if the lower priority source has 'better' or more complete data.

Not EPG sources. EPG entries IN a single source.

Example:

Your EPG is come from IPTV operator,
and "not in stream" thats why you have option to select with source to select.

update to latest.

Let me be more precise. (And I'll use TVH terminology.)

My provider supplies multiple "muxes" of "The Weather Channel", with each "mux" containing one "service". They are from different sources, but essentially the same broadcast.

The EPG I get contains one entry per "mux" (or "service" in my case). They show up under "EPG Source" as selectable entries.

I noticed that I can select multiple entries, not just one.

I understand that EPG grabbers have a priority assigned to them, and if I select ONE from multiple grabbers, they would be prioritized accordingly.

My question is: What does TVH do when I select multiple "EPG Source" entries from the SAME grabber for a channel?

p.s. saen: What do you mean "update to latest"? I just installed TVH a few days ago on my Pi4 running Raspbian Buster using TVH from raspbian-stretch stable.