Please always have a look at the provided example scenes first, in this case Spine Examples/Other Examples/SkeletonUtility Ragdoll that comes with the spine-unity runtime. These are working examples with code provided, any thirdparty tutorial videos might be outdated or obsolete.
From the provided RaggedySpineboy.cs example code you are most likely missing the ragdoll.SmoothMix(..) line. If you want to avoid that, you could issue a call to skeleton.SetBonesToSetupPose(); without any transition.
JuiceTin लिखाHow can I sort of disable IK on the weapon temporarily so it moves with the body?
To reduce the influence of a constraint you reduce the Mix value of it (it's just a shorter name for Influence). You can either key the Mix value of a constraint in an animation in the Spine Editor, or set it via code, e.g. ikConstraint.Mix = 0;.
