Well I seemed to have found where the problem lies, but noe solved it.

In the song it starts with first 4 bars as drums only and next 4 bars as drum and bass only.
This was achieved by entering Em.d for drums only and Em.db for drum and bass.

Instead of using this method, I tried using the MUTE facility in the Bar Settings.
Then saved the file and re-loaded directly from the .SGU file and everything played as normal.

As I said, I have got over the problem but necessarily solved it.

Maybe PG Music has some more suggestions based on this latest info.

BIAB 2017 Everything, RB 2017
Lenovo All-in-One. i5, 8gb Ram, 1 TB SHDD, Windows 10
Presonus AudioBox,Studio One 3, Behringer Xenyx302,
M-Audio Axiom 61, Samson Graphite 49.
Lenove Flex 15, i3,Windows 10