Hi,
This sounds like an issue with the client-server communication, where the client (your browser) was able to retrive the list of submissions, but not the corresponding rows (except for the ones in the preview, ie. those of the most recent submission). When that happens, your page “sees” the list of submissions in the cache but does not realize the rows are missing, so it won’t try to download them again if you just click on “Download” again. You need to refresh the page to clear the cache so your browser tries downloading the rows again (and hopefully the same problem does not happen again)
Jeremy