DIAGNOSIS A weak or failing cell in the battery pack. The BMS (Battery Management System) is cutting power to protect the pack.
FIX Try a different, known-good Greenworks 40V battery. If it runs fine, the original battery is defective. Contact Greenworks for warranty service on the battery.
IF THAT DIDN'T WORK The problem could be in the saw's battery terminals or wiring. Check for loose or corroded connections where the battery slides in.
HEADS UP Do not try to disassemble the battery. Lithium-ion packs can catch fire if damaged. Warranty is your only safe option.