Looks like a case of bad embedded metadata.
Probably added by whoever encoded/uploaded your files.
If your library is using the Plex Movie agent you can disable this for the future by disabling Prefer local metadata when editing your library (⋮ > Manage Library > Edit... → Advanced; you might need to refresh the metadata of existing items for that change to apply).
With a legacy agent you might need to disable the Local Media Assets source in Settings > [Server Name] > Agents or lower its priority for the applicable agent.
Alternatively you can obviously also clean the embedded metadata of those files – though I guess this might be more cumbersome.