It sounds like an adjustment, most likely of the threaded fitting where the housing ends on the RD. Turning this in either direction effectively lengthens or shortens the cable fine tuning the position - trim - of the derailleur in each gear (lever click).

Hang the bike with the rear wheel off the ground and turn the adjuster one full turn outward. That should make the RD shift to larger sprockets more effectively and to smaller ones more sluggishly. If you turn it inward the opposite happens. Your goal is to find the adjustment with the best balance between up and down shifting, which should solve your problem.

There are other possibilities including chain/cassette wear, cable friction, mis-aligned hanger or a problem in the lever whereby it doesn't stay clicked in position properly. Start with the basic adjustment, and if that doesn't solve your problem you can move on from there. There are a number of good guides on derailleur adjustment available on the internet including some videos which you'll find to be very helpful.