Yes, calculators are made from plastic ^^

[Stefan]

(02-23-2014 12:57 AM)Steve Simpkin Wrote:  Did the same multiple 10 x sqrt of 11111 test (quick presses) on a Casio fx-115ESPlus and a Sharp EL-W535X. Neither calculator lost any keystrokes.

Did you have it in "Math2D" mode (this "natural display" mode)? My 991ES-Plus does definitly loose keypresses. This key-press-loosing is also frequently mentioned in reviews about the calc.
Maybe use even more sqrts to produce the lag.

Edit: My Sharp EL-W506 also gets somewhat slower when I enter a *lot* of sqrts, but it is far from being a real problem. The Casios however show this behaviour even with relatively few sqrts so that it can be a real problem.
(Note that this problem is not only with sqrts, I just use them as an example because they are easy to type. The problem occurs with every expression which is "graphically intense", because the calc has to recalculate the entire screen (that is the official answer from the Casio support).