My understanding (now) is that the 4" vinyl covering on the top riser is sagging.
If you and I received the same adhesive, it's either inappropriate for the task or misapplied - possibly too thick.
Short of removing the vinyl, cleaning it and its mounting surface, and replacing the adhesive, I'd expect SS screws would hold it. However, I wouldn't screw it without checking what's beneath. Because of the tile riser, that might be all you've got.
If you can't screw it, maybe 3M VHB tape after cleaning both surfaces would do the job - and in a concealed manner. It's powerful stuff.
2018 FR Berkshire 39A