Tvheadend

Hi,
I have channels using DVB-C, DVB-T/T2 (some encrypted, some not) and IPTV.
I have specific channel available from DVB-T and IPTV services.
When no other channel is used and I choose this channel, tvheadend will subscribe to IPTV service.
I see this in log:

subscription: ...: "HTTP" subscribing on channel "...", weight: 100, adapter: "IPTV #1", network: "M3U", mux: ...

When I'm already watching on the other device some channel from the same DVB-T mux and then I choose the channel that is available in the IPTV,
tvheadend will still subscribe to that DVB-T service
I see this in log:

subscription: ...: "HTTP" subscribing on channel "...", weight: 100, adapter: "SAT>IP DVB-T Tuner #...", network: "DVBT", mux: ...

Is there some way to always prefer IPTV? I tried to set the priority but it's not working and I don't understand this "priority" and "weight" problematic fully..