I found a bug in ASM6. After adding a "JSR somelabel" to a label which appears later in the source file, some stuff involving the current address $ breaks. I would add ".org $" as a workaround, and that worked.
So I'm using a series of INCBINS to make a patch.
When I have a construct like this:
$ = $8000
OLDADDR = $
$ = $6000
incbin FILE.bin , $ - $6000, $70D2 - $
;some data here
incbin FILE.bin , $ - $6000, $7461 - $
incbin FILE.bin , $ - $6000
$ = OLDADDR + $ - $6000
incbin FILE2.bin , $ - $BAC0, $C000 - $
I get an error in the last incbin line. The error goes away if I put ".org $" after the jsr SomeLabel.