Some times when I add songs to my playlist they work great; after a time, commonly a long time, 1 or two have failures to play, I know there's nothing wrong with songza.

"We aggregate content from a few sources, and the results are mixed. Sometimes there are original versions, mash-ups, live versions and more."(Scott Robbin)

I think, maybe the reason of this problem is that the location of the file is currently indisposed, or maybe, they just erase the file from the server.

This is what I do to solve this unplayable song, I search the same song, listen to check that song is the right one I want, then erase the old and add the new one.

Doing this I found maybe useful to have a feature who do it a little bit more automated.

Maybe a submenu within the button of remove that appears when click in the name of the song, something like... -remove, -search replacement... or something else, and if you click on it (search replacement), songza makes a search who matches your song, then you can add or replace the old song with the new one. (maybe if the song already exists a button asking for replacement)

Sorry for my poor english, I hope to have explained my self well, it's a little bit hard to me, I am currently studing level 1, hope to be better one day, hehehe

Nice Day!