Are you using Dropbox? There seems to be a problem either with Dropbox itself or a number of hosts in North America. What we see in the log files is claims of implausible upload speeds (20MiB chunks being uploaded at 0.5 seconds; that's impossible unless you're literally connected via a Gigabit local LAN connection to Dropbox' server which is the implausible part) and a final error on upload finalisation which matches what you see, saying that the offset is incorrect i.e. the data uploaded does not match the amount of data we have been sending.
If you have set up a transparent proxy on your server, e.g. Squid or Varnish, for outgoing HTTP(S) connections, i.e. connections made by your server to other remote servers, please make sure that you are NOT caching the responses of POST and PUT requests, and that you do include all URL (GET) parameters to the caching key. Anything else will break uploads to any remote storage provider.
If you have not set up a transparent proxy, please let us know. This would confirm that something is wrong with Dropbox in North America. We've only seen this problem coming from US and Canadian users, and we have been unable to reproduce this from Europe where we're based.
In the meantime, we'd recommend using a business-grade file hosting solution such as Amazon S3, Wasabi, BackBlaze B2 etc instead of consumere-grade storage providers (Box, Dropbox, OneDrive, Google Drive -- even their "pro" or "business" offerings are still the same consumer-grade technology they sell to individuals, just with a higher capacity limit). Business-grade file hosting doesn't have the reliability issues we've seen with consumer-grade storage providers the past 15 years.
Nicholas K. Dionysopoulos
Lead Developer and Director
🇬🇷Greek: native 🇬🇧English: excellent 🇫🇷French: basic • 🕐 My time zone is Europe / Athens
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