Single episode file contains all episodes in season

Sonarr version: 3.0.4.1023
OS: Windows 10 Version 1909 Build 18363.1198

I’m running the latest version of Sonarr v3 and am using NZBHydra2 as my Usenet Indexer and NZBGet as my Usenet downloader client. It is generally working fine but sometimes it has an issue when downloading a whole season where it reports “Single episode file contains all episodes in season” in Sonarr and flags it as “Downloaded - Waiting to import”.

The episodes are individual episodes within the downloaded folder but are named in the format 'abc.xyz.xxxxxxxxxxxxxx.mkv" where all the xxxx…'s are a hexadecimal number, eg. ‘abc.xyz.2b507fcee59904.mkv, abc.xyz.6e55a97dec1256.mkv, abc.xyz.09c209b32db803.mkv’, etc. There doesn’t appear to be any reference between the randomly named files and the actual episode number. I can manually run the episode and view it, and can usually deduce what the episode is and then rename it, after which it will be automatically transferred to the appropriate media folder. Sometimes the Title metadata has the episode details which is very helpful, but usually it’s a matter of running the file and comparing it to the existing episodes, which can be very time consuming.

From what I have observed it always seems to be caused by releases that end in “-xpost”, eg. “AHS (2011) S04 (1080p BDRip x265 10bit DTS-HD MA 5 1 DrainedDay)[TAoE]-xpost”.

Can anyone suggest why this happens and how I can automatically match the random filenames that are being downloaded to the correct episodes?