Could you possibly pull it forward slightly so the edge is exposed to the interior of the cabin and use some adhesive on the overly exposed edge and then fold and hold it back into place? Id advise taping off the exposed area as that spray adhesive is a huge pain in the ass. I remember using it on my E46's and was about ready to tear the shit out and have the whole headliner redone/replaced. I removed the sliding sunshade on all of my e46's the second it happens. I may find myself doing the same thing on the E70 when this starts.

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2010 X5 3.0 X-drive Titanium Silver/Black
2018 Ford F-150 Platinum Crew
2010 528xi (His)
2017 M2 Manual (His)

Former Headaches:
2008 X5 RIP
2015 M235
2013 135is
2009 535xi Wagon (JUNK)
2007 530xi 6spd CPO Sport (Best Damn Car EVER)
2011 335xi M-sport Coupe 6spd (Sex on Wheels)
2010 550GT "CPO" (Junk)
2012 X5 35d "CPO" (More Junk)
2004 330i ZHP Sedan
2002 325xi Wagon
2000 323i Sedan
1998 M3 Sedan
1992 325i Sedan