On a fresh install on different hardware, the problem has disappeared. A test recording was available as soon as it was done, and is watchable in NextPVR.
If there is any other information you want from the failed machine, let me know, otherwise I'll rebuild it again and see if it was something about the install, or something unique about the hardware platform.
I'm guessing this error was also related to the 'database locked' error you had in your other thread. ie, the recording service did the recordings, and tried to update it's status in the database, but the database was locked so it was unable to perform this update.
I'm not aware of a scenario that can lead to this database locked error, but I'll keep an eye out for it in any logs in case there is something lurking that needs immediate attention.