Apps were slowing down considerably and got an e-mail from iFixit about older Apple batteries causing that very issue.
Lesson: ALWAYS review the repair guide before starting a new project.
I had just completed a screen and battery replacement in an I-Phone 6S and figured I could just open my SE before looking up the SE repair guide...Bad Idea!
The SE has a cable from the home button on the Display side to the logic board/backside that has to be disconnected to open the phone more than an inch.
My super suction cups allowed me to get a good enough grip to pull the phone apart 3 inches, snapping the home button cable.
The good news, iFixit got a new home button to me in 2 days and the home button was replaced in 15 minutes.
REVIEW THE REPAIR GUIDE BEFORE STARTING ANY NEW REPAIR!!!