I have an 01 es rancher that we bought new, has 6000 mi. on it now and has been awesome. Mine did the same thing, usually would up shift no problem then once it got to fifth gear you couldnt downshift, emergency shifter worked no problem and if you shut the key off then back on you could downshift it. It ended up being a computer sensor. We replaced that and it worked fine. Also when it stopped shifting the speedometer would quit working.