Ok, I didn’t know that - I guess the ‘learning’ videos I watched where a little out of date.
Nonetheless, I have tried that dialog but it doesn’t affect anything on the PCB so it isn’t a route to fixing anything unfortunately. I edited the properties of the part in the Schematic and changed the reference field from “U15” to “U15” (yes, the same value), went into PCBNew and used that dialog - it does want to change the footprint reference from U8 to U15. So that’s one avenue I suppose: manually edit the hundred parts or so on my schematic to set their reference to the existing value.
If I look in the schematic file in a text editor then I can see this for a different part:
$Comp
L CustomSymbolLibrary:OPA4192 U3
U 1 1 601C9CEE
P 8800 3700
AR Path="/601C9CEE" Ref="U3" Part="1"
AR Path="/6011D101/601C9CEE" Ref="U10" Part="1"
F 0 "U10" H 8800 3950 50 0000 C CNN
F 1 "OPA4192" H 8800 4050 50 0000 C CNN
F 2 "Package_SO:SOIC-14_3.9x8.7mm_P1.27mm" H 8850 3400 50 0001 C CNN
F 3 "https://www.ti.com/lit/ds/symlink/opa4192.pdf?&ts=1589815702512" H 9050 3850 50 0001 C CNN
F 4 "3117605" H 8800 3700 50 0001 C CNN "Farnell Code"
F 5 "Texas Instruments" H 8800 3700 50 0001 C CNN "MFR"
F 6 "OPA4192ID" H 8800 3700 50 0001 C CNN "MFR Code"
1 8800 3700
-1 0 0 1
$EndComp
Note the two AR Path statements which have a different reference: in my schematic, the part is U10; on the PCB it is U3.
For the part I manually changed to U15 (from U15) it looks like:
AR Path="/601CA0BC" Ref="U15" Part="1"
AR Path="/6011D101/601CA0BC" Ref="U15" Part="1"
So the two references are now in sync.
And now I have an idea about what might have happened. I started with a project with one sheet; then I changed it to have two hierarchical sheets and copied parts of the original sheet into one hierarchy and the remaining parts into another hierarchy then deleted the originals. The first AR path probably refers to the part as originally created and the second refers to it in the sheet (/6011D101 is the unique id of the hierarchical sheet.) There has been a re-annotation since I copied.
I don’t know which reference in the schematic is correct - should there be two entries for AR Path or just one? Is there a better way of fixing this than manually editing files/re-editing parts in the schematic?