I have custom m3u and have used the standard and custom channels tags to get it all mostly working correctly, but tvc-guide-placeholders seems to have no effect. I really want to use tvc-guide-placeholders="false", but also tried "0" and even "7200" for two hour blocks as is listed as an example. I have no clue why it's not working, there is nothing strange in the log.
Update: After wrestling with this for a some hours, just after I posted this, I went and refreshed the guide data (even though this particular source doesn't use it) and it seemed to resolve the issue. 