Forward & Back Arrow Keys Not Functioning Periodically

To Whom It May Concern,
Hello! Hope you're doing well today. This all stems from the latest update. I am having the following issue:
When I use up & down arrow keys (default function) to jump between my different clips within a given timeline...   It is then fully poreventing me from using the back (Left) arrow key to go the very last frame of the clip immediately before it. Never had an issue with it before today's update. 

So, once more, I use DOWN arrow to jump forward through the timeline & then try to jog it back by one frame and it will not navigate back to the previous clip as it has always done in the past. 

Do you have suggestions? Thank you for your time.