Sounds like you may be having the same issue I had on my 2008 LC. Whenever i clipped the back plastic in, the front would slightly rise up. Whenever I clipped the front clips in, the back clips wouldn't fully click. I blamed in on my 08 plastic maybe being slightly deformed from years of sun, or else the 50 plus times I installed, and un-installed this plate, maybe the plastic clips just didn't clip as secure as a new one. I debated buying a new factory speaker grill cover, but thought the issue could just as likely be the female portion down under the grill not grabbing the clips secure enough. Secondary issue was same as every early LC, the front edge I wished matched the curve of the truck.
Curve issue here was my "fix". Just a little strip piece of 1/8" rubber with some adhesive on the back. I'll probably try to get thinner rubber at some point but I notice it a lot less because at least it curves and covers that front gap.
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Now the bigger issue being that the clips wouldn't fully click in both the front and the back at the same time took me a lot longer to figure out as I couldn't find anybody else who'd had this issue. For this "fix" I sourced 2 longer bolts, and found there are 2 areas of factory plastic under the speaker towards the front edge that I was able to tap a couple threads into, then screw these 2 longer bolts into that to pull the front edge down. I'm over 6 months out and have had zero shakes or rattles or issues now. Basically saying i clipped the back edge in first (by the windshield), then used these 2 longer bolts to screw in the front edge. No pics of the underneath but if you look straight down while you have the plate out you can probably see the area I screwed into
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