Xtrend ET10K
I couch upgraded to 6.4.009, the image installed and the box rebooted.

The front panel display corrupted - a series of diagonal white dotted lines.

A reboot did not cure the problem.

Putting the box into deep standby, switching off at the mains and switching the power back on around 3 minutes later did cure the problem.

As I've found over the years, a complete cold boot (power totally removed for a few minutes) cures some annoyances found after an image update