(I originally reported this bug together with a few others in a different thread. To comply with the guideline of reporting each bug in its own thread, I decided to report those bugs again in their own threads and delete the original one.)
If any version of NERVE.WAD is loaded alongside the BFG, Unity, or Xbox version of Doom II, then the episode names ("Hell on Earth" and "No Rest for the Living") aren't translated if GZDoom's language is not set to English. This is because, for these versions, the names specified for the episodes are simply the English names rather than pointers to entries in language.csv.
For example, the "Hell on Earth" episode definition for the BFG Edition looks like this:
name = "Hell On Earth"
picname = "M_EPI1"
key = "h"
The "name" field there is simply "Hell On Earth" rather than "$TXT_D2E1", so it doesn't get translated.
The exception to this is that the "Hell on Earth" episode definition for the Unity version uses the proper pointer for the name, but the "No Rest for the Living" definition does not. Also, the episode definitions for the DOS version use pointers for both episodes.
I have verified this with both GZDoom 4.5.0 and the March 2, 2021 development build (gzdoom-x64-g4.6pre-133-g996b4f9f5).