I'm running bash 4.4 beta, built from source (bash-4.4-beta.tar.gz) on Linux Mint 17.2.
!! history expansion works correctly in simple cases, but not when part of a $(...) expansion.
This problem does not occur with bash 4.3.11
The last error message shown occurred when I typed Esc Ctrl-E (shell-expand-line) after typing
"echo $(!!".
$ bash --norc
bash-4.4$ echo $BASH_VERSION
4.4.0(1)-beta
bash-4.4$ echo hello
hello
bash-4.4$ !!
echo hello
hello
bash-4.4$ echo hello
hello
bash-4.4$ echo $(!!)
bash: !!: command not found
bash-4.4$ echo hello
hello
bash-4.4$ echo $(!!TRACE: pid 3822: xparse_dolparen:17: ep[-1] != RPAREN (33), ep = `'
TRACE: pid 3822: xparse_dolparen:17: base[8] != RPAREN (33), base = `echo $(!!'