Upgrade to 1.9.0 failed

Was trying to upgrade to 1.9.0 from 1.8.5 and:

admin@ubnt:~$ add system image https://dl.ubnt.com/firmwares/edgemax/v1.9.0/ER-e50.v1.9.0.4901118.tar
Trying to get upgrade file from https://dl.ubnt.com/firmwares/edgemax/v1.9.0/ER-e50.v1.9.0.4901118.tar
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
 89 76.5M   89 68.5M    0     0  4764k      0  0:00:16  0:00:14  0:00:02 4614k

It froze here. SSH locked up, couldn't reconnect. DNS forwarder stopped responding. Active connections through the router were still working but I could not connect to it at all.

Needed to physically power cycle it.

Lots of disk space, had already deleted the prior image.

admin@ubnt:~$ show system image
The system currently has the following image(s) installed:

v1.8.5.4884695.160608.1057     (running image) (default boot)

admin@ubnt:~$ df
Filesystem           1K-blocks      Used Available Use% Mounted on
ubi0_0                  220080     91788    123452  43% /root.dev
aufs                    220080     91788    123452  43% /
devtmpfs                127428         0    127428   0% /dev
tmpfs                   127532       132    127400   0% /run
tmpfs                   127532       132    127400   0% /run
tmpfs                   127532       116    127416   0% /var/log
tmpfs                   127532         8    127524   0% /tmp
none                    127532       644    126888   1% /opt/vyatta/config

Any other logs I can get you to help debug?

Chris