Any benefit in using Razz Berry and Great Ball at same time? Any harm?
Yes they are additive if used at the same time.
There is no data on if using a Pokeball and missing causes them to run away faster after a failed catch.
More often than not, the reason for the run away is just the higher the cp and more difficult a capture is, the higher chance of running away seems to be.
Yes, the effects are additive. This can be seen by tapping and holding on a Pokéball to see the color after throwing a razz berry, and then releasing it and switching to a great ball and doing the same thing. You will be able to see the difference in color of the ring change color (provided it wasn't green to start with).
source- personal experience
Yes, using both a Razz Berry and a Great Ball (as well as an Ultra Ball when you get to level 20+), increases the chance of capture additively.
But you have to remember that a Razz Berry only counts for the next hit. You can miss the Pokemon and keep throwing, but once you hit, if they jump out of the ball, the effect of the Razz Berry has worn off. If you keep throwing Great Balls, you're then getting only the Great Ball multiplier (which I believe is 1.5x the chance of a normal Pokeball).
So the effect you're noticing could mean that after the Pokemon jumps out, you're not using another Razz Berry to keep the chances up.