I am having this same issue since the last 5 days. I am a user in one of the server providers and anything beyond 8MB/28MB/58MB is giving this error.
Expected filesize of 10485760 bytes but read (from Nextcloud client) and wrote (to Nextcloud storage) 7774208 bytes. Could either be a network problem on the sending side or a problem writing to the storage on the server side.
The wrote size keeps changing but the expected number remains the same.