As above; it is the connector (particularly the plug on the loom side) that is usually at fault and not the regulator itself. As well as carefully checking the terminals there for damage it is probably worth whipping the tank off and checking the main wiring harness that runs along the top right hand frame rail. This is another well documented source of electrical gremlins on the XTZ as it wears through causing broken or intermittent connections and shorting, and all the wiring associated with the charging circuit runs through it.

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