Bad PEI plate adhesion to heated bed I'm (surprisingly) having a problem getting my PEI substrate to stick to the heated bed surface.  The ABS item being printed stuck great to the PEI surface.  I've not seen anyone else post on this problem, but perhaps someone has seen it.

Note, this is the PRINT SURFACE warping, not the item being printed.  That part went great with no delamination even on a large flat bottom.

I'm using 3M 468 adhesive to attach a PEI plastic sheet directly to the heated surface of my Flashforge Creator Pro printer.  The heated bed is anodized black and the adhesive is a sheet cut to the requisite 6" X 9".  It seemed fine and looked pretty good with few air bubbles when first attached, but the first print caused the edges of the PEI plastic to warp up from the corners of the bed.  

It appears that the weak link is that the PEI detached from the adhesive. While this was not uniform, removal of the PEI sheet showed that 95% of the adhesive was still attached to the print bed.

The PEI has one glossy side and one matte side, and I chose to apply the adhesive to the matte side to get the glossy surface.  Does this make a difference?

I applied the adhesive to the PEI surface just as it was after removing the protective plastic coating.  I figured this was a clean as it was ever going to get.

I'd definitely appreciate some ideas on this.
Perhaps this is due to the aluminum build plate warping/crowning as it heats?  I use a PEI print surface on my Monoprice Maker Select (Wanhao Di3), which has an 8.5"x8.5" build plate, and I've had no issues with the PEI coming unstuck.  However, instead of attaching mine directly to the aluminum heated build plate, I attached it (using 3M 468) to a piece of Borosilicate glass, which is then attached to my aluminum build plate using silicone thermal heatsink pads.  The rational for using a Borosilicate glass print surface is that a heated metal build surface is going to warp or move some, as the heat is coming from one side; the glass will not warp and so you have a completely flat surface on which to print (and the heatsink pads help make up the difference in surface geometry).  I used this 3dprinterwiki article as the basis for my glass bed mod, and applied the PEI/adhesive using another source (which I've forgotten, possibly the RepRap wiki).  While the first link is Wanhao Di3 specific, it covers the idea.  Make sure you tweak your z-endstops if needed on your particular machine, as adding the glass plat raises the bed height by several mm.

Please note that I'm theorizing - I did not ever try applying my PEI directly to my aluminum build plate, so I have no direct comparison.  But the use of glass to eliminate build plate warping/crowning is fairly well documented. See also this 3DPSE Answer.