Trouble with mesh and bones

Hey Joseph,
When a mesh lerps off the rig like that, the first thing I check is each of the bone constraints that have influence in that area. It can be a misordering of constraints or maybe you have one active that doesn't need to be. I would go through each one and toggle them on and off to see if one of them is causing it. The next thing to look at is the mesh modifiers. For the same reason as the constraints. See if any modifiers are doing something crazy before or after the armature modifier. (most of them should be set after) The next thing I would think about is you might have a parent loops in the bone hierarchy. Thats when the parent child relationship accidentally loops back into the its parent again and it can make rigs really freak out. (in fact this is an easy one to check, you may want to start with checking for this one) If you're still stumped let us know, we may need to see more of the armature settings. 

Thanks for your reply 

If you could explain to me how to check the parent loops in a bone setup I would be grateful as the mesh and the bone only have one constraint and modifier on it 

https://www.loom.com/share/6b378b53b719451182030e9e3bee3d21?sid=9ca6c839-35fd-4bb3-9df2-636fdad3d51f

1. On your IK constraint you need to set the Chain Length to the number of bones in the chain. It looks like there are 12 from the video. 
2. The IK control bone shouldn't be parented to any of the bones in the chain. You can make sure of this by selecting it and pressing alt+p->Clear Parent. 
3. To check parenting you can select the bone then in the properties editor->bone tab->Relations panel->Parent field shows what it is parented to. For the chain they should also have connected checked. 
4. Check weights: Select the mesh and towards the end that is suppose to connect to the monitor select a vertex. Then on the n-panel->Item tab->Vertex Weight panel make sure that it is only assigned to vertex groups that match the bone chain. The vertices that are all red should only be assigned to 1 vertex group. 

If that doesn't show anything then select the armature, go to pose mode(Ctrl+Tab), select all bones(A), clear all transforms(Alt+G, Alt+S, Alt+R), and make sure the mesh lines up with the bones. If it doesn't then you will need to redo the weight painting.