Seems like drop() on DA's doesn't preserve dimnames in BioC-release:
library(DelayedArray)
x <- DelayedArray(cbind(A=1:10, B=2:11))
x[1,]
## [1] 1 2
On BioC-devel, it does the right thing:
library(DelayedArray)
x <- DelayedArray(cbind(A=1:10, B=2:11))
x[1,]
## A B
## 1 2
Seems like a simple patch across to BioC-release would suffice.