Ah! You're right. The second issue was already reported back in 2015 https://lists.gnu.org/archive/html/bug-bash/2015-02/msg00060.html
Now, regarding the SIGPIPE issue. The message bash is printing just means that grep closed the pipe, so the bash process receives a SIGPIPE when attempting to write. The output of strace (make sure you use -f to follow forks) will make things easier to find out where the issue is.
