Shadows in Tunnels

Ever since shadows were added to Trainz way back when, I have had no problems with tunnels which were totally blacked out. However somewhere along the line in TRS19 shadows have started to appear in tunnels. For instance if a vehicle on a road passes over the top of the tunnel its shadow can be seen in the tunnel. In T:ANE it was OK but obviously some starter pack (or even the original version of TRS19) has now got this problem. Can anybody throw any light on the situation and is there any solution ?

This is only applicable if the tunnel type only has portals and the internal part is open roofed. Tunnels which are totally enclosed are OK.

Tony Howard