The problem occurs when you cut oversized media into a lower resolution timeline. For example, true 2K media in a 720p timeline. Then send that to Resolve via FCPXML. In Resolve, all power windows are offset and don't occur in the proper location. This appears to be corrected if you reset Resolve's master timeline resolution to match the higher-res media and then back to the original settings. Once you do that, the windows are correctly aligned.