I had a similar problem with mine when I fitted my stereo had a gap at the top, it was cause all the surround trims all need to be lined up and clipped in properly for them to all line up. From memory there is torx screws at the top that will need to come back out under the top vent take your time as it's a bit fiddly and tight. Pretty sure there is a how to remove the stereo video on YouTube I watched before doing mine.
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