Problem with LCD 128x240 pinout
As you suspect, pin 19 must be connected to a potmeter, other side to ground, wiper to pin 4. No value is specified, I always take 10k.

I think page 2 is copied from a display where pin 22 had a function, and the table lateron which lists it as NC is correct. I sell a display that looks a lot like yours, but mine has only 21 connections. You might check the traces to see whether your 22 is connected to something.