QEISTAT Register has a bit called ERROR, which is set high "when an error was detected".
I could not find anywhere in the documents information regarding "for how long does that bit stay set". Does it briefly go high during the few clocks when two quadrature signals change at the same time, and right after it it goes back to zero? Does it go high once and never goes back to low???
If it briefly goes high, the Tivaware QEIErrorGet() function would not make too much sense, unless we are lucky enough to call it right during the error.