This seems to happen with a very small number of these shields. Most likely a bug in the library which we've been trying to home in on. In the meantime, try adding an extra line to 'fake out' the driver ID, like this (around line 58 in the 'graphicstest' example):
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uint16_t identifier = tft.readID();
identifier = 0x7575;
See if the example then runs. Depending when your board was manufactured, you might need to try one of the other chip IDs, either 0x9325 or 0x9328.
Please let me know if that works for you, in which case I may have a more permanent fix shortly.