[shaktoo]

I had to follow a few tutorials and managed to setup mySQL server and now its working like a charm across 2 x Nvidia Sheilds & main PC which has the main Kodi & the mySQL server.
I had many setbacks and took a month for things to smooth out.
My main mistake was that ALL the clients ( including install on main PC ) have to have libraries setup as "smb shares " . I think this is one of the steps where I made mistake and had to redo everything.
The inprogress media widget has a lag and i wanted to bring this to someones attention but just wasnt bothered enough. ( ANS skin & Bingie )
As stated Movies are updated instantly but the inprogress shows arent updated quickly. I found that if i play an episode of whatever on one of the machine then once that episode finishes the widget updates to the appropriate episodes.
Similar things might happen on another slave kodi install. 
As klojum has mentioned I might get the skin refresh as a startup task to see if this reolves it .

When you say SMB shares what are you refering to? I currently use NFS. I just find it a whole lot easier. Sureley it shouldnt make any difference between SMB and NFS

SMB is similar sharing protocol to NFS. 
Most of the tutorials I watched  were recommending SMB , plus I had setup SMB shares and was more comfortable with it so went with it.
It isnt any difference and does not really matter.
what matters is that ALL the server & clients running Kodi access the server library via a share SMB or NFS . Otherwise it does not work.