I have never used the Upload command from the WebUI. So today, I thought I'd try it, with a large file.
Jethro Tull's Thick as a Brick album is divided into two tracks, representing the original LP's side 1 and side 1. Using Audacity, I concatenated the two tracks into one long track, with duration of 43:50. The file size of the FLAC file reported by my computer is 286,004 KB (~= 286 MB), nowhere near the 4GB limit.
If you want to skip all the boring details, jump ahead to the last paragraph.
In the WebUI, the Upload command allows for either a Bulk upload or a single file upload. I chose Bulk, which then prompted me to Choose File. I ignored that and selected a folder, Jethro Tull, containing one Album, Thick as a Brick, which in turn contained the one song file. The upload began, and got stuck at the 73% mark. Because I went about doing other things on my computer, I thought maybe that had something to do with the stall. So I tried again, and limited my computer use to simply writing in a text file. This time the upload got stuck at the 74% mark.
To rule out a possible problem with the source file, I went to the 31 minute mark and played it through the 73% and 74% area to near the end. No problem.
Going back to my ignoring the prompt to select a file to upload: I have been under the impression that we could upload at least an album's worth of songs at a time, maybe more. Was I wrong? Can we really only upload one song at a time?
So I went back and chose File Upload. It prompted me to enter the Album name: Thick as a Brick (1972), and the Artist name: Jethro Tull. The Jethro Tull artist folder existed previously and the Album folder is new. This time the progress wheel sas spinning but there was no indicaiton for percent complete. On the earlier attempts, the front panel showed a flashing red light. This time the red light was steady and the clock continued to count up the seconds. I clicked on Cancel to halt the upload but nothing happened. I clicked around the WebUI and it seemed to respond, but when I went back to the Upload panel, it was still spinning the progress wheel with no indication of percent complete.
My WiFi signal strength is currently -23. Software version is B2B Oct 22 2021. I've had no indication that my software might be corrupted. After the upload failure, I went back and exercised the B2: ran an Import from USB of three albums, paired with my Bluetooth speakers, played a couple of songs. All seems normal, except for the Upload command.
My tentative conclusion is that there is something wrong with the Upload command.