Test 2067.4 is failing on (at the moment only there) r-devel-windows-x86_64. Recent change to handling complex NA type seems quite likely to be related.
Test 2067.4 ran without errors but failed check that x equals y:
> x = shift(list(z, 1:3))
First 2 of 2 (type 'list'):
[[1]]
[1] NA 1+3i 2+2i
[[2]]
[1] NA 1 2
> y = list(c(NA, z[1:2]), c(NA, 1:2))
First 2 of 2 (type 'list'):
[[1]]
[1] NA 1+3i 2+2i
[[2]]
[1] NA 1 2