I've got an issue with setting up my 1976 Fender Jazz. I adjusted string heights/action (no neck adjust) and began to set the intonation. All strings came right in without much saddle movement except the E, it was sharp at the 12th. So I kept moving the saddle back but ran out of adjustment. Didn't seem to help a lot either as the 12th was still sharp and now the string itself was too high. So I thought maybe it was a bad E string. Put on new strings and same things more or less, E still sharp at the 12th. One additional piece of data, the new strings are a heavier gauge. I checked intonation on the other strings and they've moved a bit sharp at the 12th now also. I've read that the neck could need to be adjusted (flatter). Also thought maybe the heavier gauge has caused a bit more bow in the neck thus explaining the other strings now being sharp at the 12th. I know this is long but I'm seeking advice on what to do or what could be the issue. Thanks.