Thanks everyone for the input.

The guitar is a Washburn WD40S. The entire bridge was replaced due to a crack going right across. The buzz is on the large E, and seems to happen on the 13th fret, no matter where I'm playing/with/without capo.

The suggestion of raising the bridge/saddle on one side may be easiest way to go, or maybe the fret needs dressing on the 13th fret???

All your input has been helpful - the humidity level is low, but will keeping a humidifier in the guitar on the stand rectify the fret buzz problem, or is more work required?

Continued feedback is very welcome!

Thanks again!