One last idea.
When I am done using my player, I usually push “Pause” and then then power off. Then, when I manually power up the player, it will still be in pause mode.
When I do not push “Pause” or when I use the Sleep Timer for auto shutoff, the next time I start the player, it will resume playing where it left off.
Maybe these alternate conditions also affect the player when it is off and then connected to an AC charger?