Waveform of a SR Latch
The input's three gates ensure that only 'S' or 'T' can be high at any one time.

If 'S' is taken high then 'V' should latch high. If 'T' is taken high then 'U' should latch high. That is to say, taking an input ('S' or 'T') high forces the opposite gate's output to latch high.

So, the 'U' &amp; 'V' labels on the timing diagram should be swapped over with each other. But, ignoring this then the last pulse is not exhibiting the latching action that should occur, as you have noticed. Taking 'Q' low, forces 'S' &amp; 'T' low but this shouldn't cause a change in either 'U' or 'V'.