"Up" arrow to repeat last command returns a penultimate command every 2nd try

1) echo 1, enter
2) echo 2, enter
3) up arrow - expected "echo 2", actual "echo 2", enter
4) up arrow - expected "echo 2", actual "echo 1"

and you can cycle through this - when you execute the "echo 1" from step 4, then hit the up arrow, you will get "echo 1" again.. but then if you execute that and hit up arrow, you will end up with "echo 2" again