When trying to make rennet in brew kettle, the flame icon flashes repeatedly and no rennet is made. Stomach is accepted when dropped in. I'm on 1.12.2 latest, using forge 1.12.2 - 14.23.5.2768. Other mods included in screenshot.

https://media.discordapp.net/attachments/333690296334548994/566821009034838017/unknown.png?width=768&height=754

Going to test it out ... Of note, your forge is significantly behind. We build it with version 14.23.5.2768

My bad, that was a typo. I'm running a Forge server on 1.12.2 - 14.23.5.2768.

We're unable to duplicate the issue. Tested with netherrack on fire and magma cube.

I recommend clearing out your growthcraft configs and see if that fixes the issue.