Audi upload bug
That sounds like some formatting issue with that specific audio file you tried to upload. You can send it to support(at)lingq.com and we will take a look.
For me it seems more like a bug because I got the 7 audios from an audiobook and all the files that have a playtime longer than 10 minutes upload without a problem. There is just this problem with two audios shorter than 10 minutes.
I can't reproduce the issue on my end, it must be something related to those two files. Please send them over and I'll take a look.
Thank you! I solved the problem.