Elements 2020 time stretch headache

Hello, I'm using Premiere Elements 2020 to edit a 3 track video.  I have each the footage of my camera angles sync'd up on three tracks and I'm able to switch back and forth between camera angles by adusting the opacity of each of the videos on the separate tracks.  There is a place in one of the videos where I need to time stretch a scene (no sound).  I split the clip on either side of the scene in question to created a new clip that i want to stretch.  I then trimmed the clip on the right by dragging the red bracket to the right thinking I was making room for the time stretching.  As expected, there was now a space on that track. to allow for and extension of my new clip.  I attempted to then timestretch the newly created clip.  I wanted to slow it down.  I changed the speed to 50%.  As expected, the new clip increased in length by the appropriate amount.  BUT, and here's the problem (sorry for the long preamble), instead of the clip just filling in the gap, it pushed the right-hand trimmed clip ahead on the timline by the same amount.  And to make matters worse, it also pushed the clip on another track ahead by the same amount.  This is not a desirable outcome as now two of my three  tracks are out of sync.  I just wanted to create some space on that track for a slow-down of part of the clip.  
What am I doing wrong?  What is the simplest way to accomplish slowing down part of a clip while maintaining sync in the rest of the video.  Thank you for your time.  Any and all suggestions welcome.