bash pipe redirection gets stuck

[long at rule.lv]

Dear all,
I stumbled upon a problem where multiple pipe redirection occasionally get
stuck when trying to get sha256 sum of a stream.

You can try to reproduce the problem if you have /usr/ports/shells/bash
installed (output redirection used in this command is possible only in
bash).
Create temporary test file with command: "dd if=/dev/urandom of=/tmp/file1
bs=1k count=10"
And the command I'm using is:
/usr/local/bin/bash -c 'cat /tmp/file1 | tee >(/sbin/sha256 >
/tmp/file1.sha256) > /tmp/file1.copy' ; echo $status

Command gets stuck about once in 20 executions.
top output when command gets stuck (irrelevant processes removed):
  PID USERNAME    THR PRI NICE   SIZE    RES STATE   C   TIME   WCPU COMMAND
84073 HappyUser     1  52    0 17612K  2268K wait    0   0:00  0.00% bash
84154 HappyUser     1  52    0 10084K   844K fifoow  1   0:00  0.00% tee

And more strangely, I can reproduce this problem on 9.0-RELEASE and
7.4-RELEASE-p6, but couldn't reproduce on 8.2-RELEASE-p4.

Thanks for any pointers/explanations,
Normunds