I checked the battery and it reports as fully charged and the multimeter says it is at 57.1 volts out of the supposed 58 volts, which seems fine to me
Is that the voltage checked right after charging? Or did you check the voltage only after attempting to run the tool and it stopped?
I don't know the exact specs for the Echo batteries, but fully-charged 57.1 ...
I have had 5+ batteries brought to me that show full charge to no charge but do similar or slightly less.
In all of them they had been heavily discharged according to the owners.
All of them had melted a solder joint connecting to the battery pack. I was able to reflow the solder and save the packs in all of the cases.
2 of them showed no charge but it was ...