Thank you!
I checked the tap-test gently with a screwdriver. The right pickups are positive as they should be ... however, in positions 2,3,4 I get a loud "tonk" from the middle pickup, and the bridge and neck produce similar loud tonks in 4 and 2 respectively. But in 1 and 5 positions, the middle is appropriately silent, but the humbuckers only produce a faint click (both rows exactly the same).
The wiring seems correct from the charts I've seen ... Neck: Red-8, Green-3, Bare-V.Pot, B&W braided ... Middle: White-2, Black-V.Pot ... Bridge: Red-6, Green-1, Bare-V.Pot, B&W braided ... other switches (it's a YM-50) 4-V.Pot 3, 5-empty, 7-V.Pot (i.e. ground)
So ... although the "connections" seem OK ... the big drop in sensitivity on the tap test of both solo (but not when paired) humbuckers seems to be wrong?
I don't know how to interpret this?