Can not delete and close gap - But with a twist!

Hello!

So I know there have been many posts about this and I understand usually when the reason delete and close gap will not work is because another layer/music is on the timeline.

However for me, this happens randomly.

When I initially put the music on the timeline,  I am able to edits my clips fine, using both trim and the cut features. 

However I will then loose this ability, so gaps now stay open when i have trimmed, but not for every clip.

Right now I cannot trim any clips except for the very end one.

The music layer has multiple music clips on.

I'm stummed and confused.  Any help would be great!