Torrent cannot complete on transmission-remote in docker container due to continuous deletion of data

Question

transmission-remote is running in a docker container with good internet connection, downloading a file with sufficient seeders. As the torrent approaches 99% completion, the download speed will slow, and then the completion rate will be reduced to 98% or even 97%, before climbing back up. Similarly, the total data will fluctuate between 4.83 and 4.88GB. This problem previously occurred at lower levels of completion, but was mitigated by removing other torrents. This increased the download rate, but didn't stop data from disappearing. The data is stored in a host volume mapped to a container directory.

What could cause the data to disappear, and how can this be prevented?

Not sure this is relevant, but the transmission container connects to the internet through another container running nordvpn.

transmission-remote version 3.00 docker version 20.10.10