Hello,
I am using spongeforge-1.12.1-2444-7.0.0-BETA-2500 & forge-1.12.1-14.22.0.2444-universal on Windows 10, clean files.
I got this error when I added spongeforge-1.12.1-2444-7.0.0-BETA-2500.jar to the mods
[01:22:05] [Server thread/WARN] [FML]: Missing English translation for FML: assets/fml/lang/en_us.lang
[01:22:05] [Server thread/WARN] [FML]: Missing English translation for spongeapi: assets/spongeapi/lang/en_us.lang
and every time I add a new mod I get the same for it
[01:22:05] [Server thread/WARN] [FML]: Missing English translation for griefprevention: assets/griefprevention/lang/en_us.lang
[01:22:05] [Server thread/WARN] [FML]: Missing English translation for luckperms: assets/luckperms/lang/en_us.lang
[01:22:05] [Server thread/WARN] [FML]: Missing English translation for nt-rpg: assets/nt-rpg/lang/en_us.lang
[01:22:05] [Server thread/WARN] [FML]: Missing English translation for nt-core: assets/nt-core/lang/en_us.lang
I tried older builds, I also tried with 1.11.2, same problem. This problem does not exist on Linux with the same build.