What could be the problem of uploading a file from FTP to the 1s Bitrix site?

Question

1C-Bitrix

Between 1s and a site on 1s Bitrix, files are exchanged via FTP, it is customized. Until recently, everything worked, but at a certain point (Sunday), the file with the remnants stopped loading. At the same time, the goodies file with goods, a separate one with prices, are loaded normally. Such a moment that while the files are being loaded, they are in the tempo folder, the rest get there, they can hang there for 4 hours (although it used to be about an hour), and then they do not go to the archive, which usually means a successful download. and as a result, the file with the remnants generally disappears from ftp. And another such moment, we have the concept of full unloading and partial. Full is the entire amount of data being loaded, partial is only those that have been changed. And now, when unloading a partial, the remnants are safely loaded. Some kind of paradox, no one can even understand on whose side the error is. But I suspect