As per title - if you pick a goblin up in a cage from Supplementaries you can then never release them, they just stay stuck in the cage. Normally you can release mobs from the Supplementaries cage by right clicking.

Same pb here, on cisco fantasy mediaval modpack 1.19.2 forge, supplementaries last version 2.4.20 and goblin trader last version 1.8.0
I can't release the goblin from the cage

Make sure that it isn't a conflict with "magnumtorch" mod... even after removing said torch it causes the issue... It can be confirmed that this is an issue by checking if you can place the caged mob higher or lower than where the original torch was placed... Also checking other chunks around the original area might help too with troubleshooting and figuring out what the issue is...

Hope this helps, as it fixed my issue.