…also had this problem while fixing a Z3. the tapes are often not thin enough so that the display has no clearence with the middleframe, or the tape slided away while letting the display slide into its position on the frame.
So i also can recommend fixing by fluid glue for displays. There are several to buy online for small amount and you also can order spare displays delivered with fluid instead of tape.
After i tested the new display in “lose” position i dismounted the middleframe from all components and first glued the display on it (you often get fixing-descriptions where the mainboard etc. remains in the middleframe while changing the display). This avoids anything beeing in the way of a propper sitting display and more than that it avoids the effect that after connecting the display with the mainbord the flexcable is giving back the energy bounded in it cause its bended for the first time.
Greetz from Berlin, Markus