I got this in my server console.
https://pastebin.com/dkkYq4Ee

I use Minecraft 1.12.2 and the new forge 14.23.5.2855.

Thanks for the report. 1.12.2 is a very old version that is no longer supported. I will look into releasing a patch but that may not happen. The issue is caused by malfunctioning JEI support, installing JEI should resolve the issue.

Since this is not a fatal issue, this is definitely not getting a special patch.

Ok. Thanks.