I'm reporting the same bug that is already known for Edge 530 - https://forums.garmin.com/sports-fitness/cycling/f/edge-530/306962/bug-my-load-epoc-was-reset-after-turning-off-and-turning-on-my-device/1511272#1511272
Very frustrating overall when doing long activities with multiple stops only to lose everything. Makes the Garmin ecosystem less reliable for analysis.
Would be useful to at least having a way of recalculating the Load after the activity is done