Mine shifts smoother after the trans fluid change I did. There is anecdotal evidence that suggests that new fluid with fresh additives (detergents) will dislodge some crud that has accumulated and clog a valve body. Others scoff at that and say change it.

I wouldn't do a full flush if I were you, but maybe drop the pan and refill after putting in a new, OE filter (don't cheap out here). Also, use the correct ZF fluid for your transmission, Lifeguard6 (I think yours is a 6-speed, right?).

While you're at it, dump the diff fluid and the x-drive fluid and replace. Any 75w-90 synthetic diff fluid is fine. Use only the BMW x-drive fluid which is pretty expensive (~$50/liter -- it only takes one liter). You should reset the x-drive adaptations via BMW's diagnostic software.

__________________
Kirk
Las Vegas
2016 X5 40e Mineral White/Black Dakota Leather, ZLL, ZCW, ZDA, ZDB, ZPP, multi contour seats, rear side window shades, HK stereo
2011 E90M3, 6-speed manual