This bug was reported by fersingb on IRC, I could reproduce it.

If you have a public keyring in the .kbx format exporting a key with the full
keyid produces an endless output sttream.

To reproduce it I can import any key into a newly created gnupg homedir.
When exporting this again using the fingerprint as identifier the bug is triggered.

My usual gnupghome was automatically migrated still has a pubring.gpg and works.

Setup:
FAKEHOME=$(mktemp -d)
gpg2 --armor --export CA308D95A6332F7056B4DFD194F78CF1265059CD | gpg2 --homedir
$FAKEHOME --import

Triggering the bug:

gpg2 --homedir $FAKEHOME --armor --export CA308D95A6332F7056B4DFD194F78CF1265059CD

The short fingerprint works:

gpg2 --homedir $FAKEHOME --armor --export 265059CD

My current version is yesterdays master (2.1.1-beta45) but the original reporter
used gnupg-2.1.0.