jornise

All of my cardoors lock/unlock with the driver's side master button except the front passenger door. Anything I might be able to look at before bringing it in and possibly being told it's something very expensive? Thank you in advance for any help.

I hear a dull clunking noise in the rear passager side when making a slow stop ( although not every time ). I seem to notice it more after making a left turn, although that could be because I notice it most when pulling into my garage. At 30K miles (in 2008?) I had the rear differential fluid changed and it stopped the noise at that time. Yesterday I ask the technician to change it again in hopes of stopping the noise, but he said it was crystal clear and full. My car is a 2005 CRV with 70k miles. I'm almost tempted to have it changes anyways....I'd appreciate any help or suggestions. Thank you.