I did as you suggested. Before looking for these channels, I stopped the TV service and delete old logs. After starting the service, I once made a channel search and store all the log files along with files ts.Detection if channel is FTA (free to air or unencrypted) is not part of IPTV filter. I recommend you to save raw TS file (e.g. in configuration file of IPTV filter set DumpRawTS to 1 and try to scan problematic channel, filter probably produce two files, the bigger one is right) and post your problem with encryption detection to support forum.
Encryption detection RAR file
For example, I did scan for 2 channels, which are recognized correctly.
Encryption no detection RAR file
I hope this information will be sufficient.
Ukraine