Isn't it the same problem I reported in
https://www.mobileread.com/forums/sh...&postcount=680 (third issue, see screenshot). Brucelee's comment a couple of posts below, disable the custom theme. I kept seeing it on and off at subsequent CR OTA updates, but alas, CR options, disable custom, exit CR, reopen, ok.
Something of the theme improved across the couple of OTAs I had - e.g the dictionary button icons are now nicer than those I got when I got onboard.