Post screen shots.
Here are screenshots. I tried a couple of tests and seems that the bit rate it resets to is random. For instance, I just set the bit rate to 35 and clicked OK. Then I went back into the settings and set it to 25 and clicked OK. Then I started the compression and it had reset itself back to 35. Then I deleted the source file, re-imported it, used the same blu-ray preset, and changed it to CBR 23mb/s, but when I started the encode it had jumped to 25. I stopped it, went into the settings, changed it to 18 and clicked OK. Then I went back into the settings and it was back at 25. Here are some screenshots of what's going on, taken within a couple seconds of each other.