audio splits when I add images to timeline elements 2023

I'm adding /inserting photos and effects to the timeline. when I do the audio track and the music track splits and I can't detach them from the timeline with photos. the delete and close gap is greyed out. I've tried grouping and ungrouping in case the audio and photos are connected somehow. Please can someone help? I feel sure there is something simple I can do! thanks! attached pictures show everything is good, then a picture after I've inserted an image - the audio splits...have to admit I'm going crazy here !!