When I sent the forcemerge command you see below, the template bug was
blocked by a closed-and-archived bug and the other bug wasn't.
Debbugs seems to have become slightly confused as a result.

Observing that something had unblocked the template bug, I resent the
commands and then it worked.

Thanks,
Ian.

From: owner@bugs.debian.org (Debian Bug Tracking System)
Sender: Debian BTS <debbugs@buxtehude.debian.org>
To: Ian Jackson <ijackson@chiark.greenend.org.uk>
CC: ijackson@chiark.greenend.org.uk
Subject: Processed (with 1 errors): already signed 2
Date: Sun, 03 Aug 2014 18:03:09 +0000

Processing commands for control@bugs.debian.org:
Limiting to bugs with field 'package' containing at least one of 'dgit'
Limit currently set to 'package':'dgit'
Bug #731635 [dgit] want better error message for already-signed files in push
Bug #753256 [dgit] dgit: "syntax error in  at line 1: PGP signature not allowed here"
753256 was not blocked by any bugs.
753256 was not blocking any bugs.
Added blocking bug(s) of 753256: 735975
Failed to forcibly merge 731635: can't find location for 735975.
Stopping processing here.

Please contact me if you need assistance.