Slow animation + First Time Step Stays

Hi all, for some reason the first time step is staying in my animation no matter what and is overlayed with the ongoing animation. This shows up as a pink line at the beginning in time manager. All my settings have been reset to the standard settings, not sure why this is happening? And, it is going incredibly slowly and for some reason is only using 3% of my CPU (computer is not being overloaded). It is a large dataset, but I am not sure why it wouldn’t be using more CPU? My version is 5.12.0 - RC2 - would appreciate any help!