I found mpv as a videoplayer pretty good at looping small clips seamlessly.
OFS uses mpv and I’d say it loops pretty seamlessly.
There are plenty of script players for the OSR2 which can use mpv but I’m not sure about the looping capabilities of the individual players.
MultiFunPlayer allows you to pass arguments to mpv.
If you add “–loop-file=inf” you get pretty good results.