I had a similar problem the second time I tried to run my new NKP 765. I thought I was destined for a trip to Concord for repairs but noticed my Legacy Remote batteries were low. After a full charge I have not had this problem again. This may be worth a check for you.
Unfortunately I do have a little gear noise pulling a 2.0 % grade with no load. So I may be calling Concord on that issue.
Thanks. No my batteries are new and fully charged. I called Butch at Charles Ro and things are being taken care of. Thanks again for the suggestion.