John Rumm wrote:

The new place has two downstairs lighting circuits, the most heavily
loaded of which (about 1050w by my quick count) [...]

1050 W, but how many VA? I.e. is there enough low-power-factor
discharge lighting in there to make the RMS current significantly higher
than you're perhaps expecting? Bear in mind that the standard guidance
is to assume Ib = 1.8 * power/Uo in the absence of more specific info.

--
Andy