Mesh got worse after installing the enclosure

So, I've had some issues getting my frame (vcore 3.1 400) to be level and square, and the mesh had around 0.17mm of variance, which was fine by me However, After adding the enclosure panels, this is what I get (Image 1) and my old mesh (Image 2). It seems like the bed is sagging heavily at the back, non supported corners, but I don't see how this can be caused by the enclosure. The center highspot, I can take as variance in the bed and adhesive (although, why doesn't it show in the old mesh as much) installation, but the bottom low spots (around -0.18mm) are weird. Also, trying to shift the frame in the front doesn't lead to significant changes in the mesh, unlike when squaring the frame the first time