SMPlayer Support Forum

As an addendum, delaying the default subtitles (dec/inc_sub_delay) also doesn't work before selecting the subtitle track in the menu.
Strangely the A-V delay (dec/inc_audio_delay) DOES work.

The problem seems to be that initially, the player uses the correct tracks, but somehow doesn't mark the tracks in use as active. Previously the current track would be indicated with bullet point/circle icon in front of it in the menu. This only happens after selecting one in the menu now.

I think this happens when using mplayer. Does it work correctly for you if you change the "multimedia engine" to mpv in preferences -> general?

It does indeed. Thanks for the tip!