You may have already found and tried these possible fixes, but just in case you haven't-
1) There's a firmware update for the docks that is supposed to resolve a number of display issues.
2) It appears that similar issues can be caused by having a defective or incorrectly-sized dock power supply. So replacing the power supply with a known-good and/or bigger power supply might help.
Though, in my case, neither of the above helped. It turns out I had a bad HDMI/VGA adapter. Since eliminating that, I've had zero display issues. But I'm guessing that probably doesn't apply to you, since my configuration is a little unconventional.
Anyway, I hope you find something that fixes it for you.
Tell me more!
Alternatively, you can do a bit of soldering/modding and put in an aftermarket 1920x1080 panel. https://nitrocaster.me/store/x220-x230-fhd-mod-kit.html
And the parts are cheap and plentiful. Get the docking station if you can, I paid 30$ for two a few years ago (top of the range dock, the one with all the connectors and 2x video out)
Also, the IPS upgrade is well worth it.