Shimano Steps 6100 loses power assist climbing hills

Having problems with bike losing power going up hill – 4 of last 5 rides. About 400 miles on bike (BMC Alpenchallenge AMP Sport). Have several 40+ mile rides with 4,000′ of elev, so it works. Now I’m not even getting 15 miles and have to turn around. Randomly loses power while going up hill, but so far it comes back on after turning around and going back down.

No error codes yet.

Did have 1 ride last year where it stopped completely & took 45 minutes to come back on. Found 4 W013 codes for that.