The Englishman

Hello & regards from the UK I own an immaculate deactivated Thompson 1928 A1 in mint condition, part of a consignment sent from the US to the USSR under 'lend lease' during the war, it has remained unused in an obscure Russian armoury for the last 60 odd years prior to arriving in the UK and being deactivated. However, despite the condition and fabulous manufacturing quality of the weapon I have noticed that the stock is a little wobbly, there is movement in the butt, which increases a little more every time I detach and re attach it. Is there a solution ?, a way of tightening the stock to the guide rails ?,there appears to be no wear atall to the metal rails although the blueing is a very slightly worn away. Do I simply accept that this happens, or pack the rails with a little wadding to take up the slack, is this a standard fault ? I would be grateful for any expert tips from any American enthusiasts with more experience than I. Many thanks for your time in answering