I first thought the keyboard should be pressed under the tabs, but when I try pushing it in there is another may be 5 mm before I can close the lid (complete stop). Feels like I am going to break something if I press any harder.. but if it is as you say, then it would explain why the plastic bends like it does.
May be I can heat up the tabs a bit to soften the plastic .. feels like a bad idea tho
Definitely under the tabs mate. Here's a picture of how it should look:

To get it under the tabs, just slide it into position and attempt to slot it in, and when you feel that resistance like it won't slot in, simply press down on the front edge middle of the keyboard (right near that bottom screw hole in the picture) to get it under those two middle tabs (this is where it is sticking).