Hi there,
I was having the same issue with some of my albums, but not all of them. It seems if the album art is high resolution, the track takes a while to load or skip. Also, the higher the resolution, the longer the wait. This is probably because rockbox has to resize the image before it can play the track.
I recommend (if you’re okay with retagging your music) converting your current album art to 300 x 300, or finding low resolution images online, then apply them to your music. After they were tagged, my music started much faster. Hope this helps.