I agree. either one of the connections on THAT reciptical is bad, or the one before it.. You may need to replace both.
I favor traditional house type devices where you bend wire around a screw NOT the "Quick Box" trash that RV makers use.
The alternative issues are: The outlet itself is bad (Medium probability) Or the wire connecting it to the last up-line outlet is bad( Probability approaches zero, That is, not at all likely)
O ne final possibility, this ranks high.. IF either of the last two outlets in that chain are in a slide. There may be one or two junction boxes..