I want to delete the highlighted section in the image below and keep the other tracks in sync with the remainder of the now shortened track. (The delete works without having to crossfade the new join)
But if I apply sync lock and delete that sector it also deletes the end of the drum track below it which I don’t want. If I don’t use sync lock everything after the delete is thrown out of kilter.
How do I get around this?

Demarcate the drum track as in its own Sync-Locked Track Group by putting it at the bottom of the project with a label track above it, and make sure the drum track is not selected.
First, Edit > Region Save.
Tracks > Add New > Label Track. The Label Track appears at the bottom of the project.
Click above Mute/Solo on the drum track and drag it to the bottom of the project (so the label track is above it).
Edit > Region Restore.
Now you can SHIFT-click on the Track Control Panels to select the restored region in all the tracks except the bottom one. You will see the Sync-Lock icon is not showing in the bottom track, so that track will not be affected by the deletion.
You could instead click in the name of the drum track and choose “Move Down” as needed. This preserves the region in the Timeline, so you don’t need the region save and restore. 2.0.6 will have “Move Track to Bottom” and “Move Track to Top” commands in the Track Drop-Down Menu.
Gale
Easy when you know how! 
Thanks a lot Gale, that’s made my day!
Sorry, I should be completely clear that the only essential tasks are to deselect the drum track and to select at least one of the tracks in the Sync-Locked Track Group above the drum track Group.
As you’ll see, selecting just one of the tracks in the Group you want to delete from will enable the Sync-Lock icon in all the tracks in that Group.
Gale
Thanks, I’ll use that refinement next time.