It seems as of ROS 5.x and ROS 6.x when updating Routerboards there are several that end up needing a physical power cycle or worse, they need a full netinstall (meaning the device has to be removed from the customer, with downtime, and brought to a shop/laptop with serial cable and windows OS).
Im not sure if these updates are not being tested across all hardware or if something else is the culprit, but with nearly 100+ routerboards deployed, over the past 6-12 months we have to be very careful when updating ROS, especially when updating from a major revision (meaning from ROS 4.x to 5 or 6, or ROS 5.x to 6). It never used to be like this.
Its very frustrating and costly to have to roll employees out to customers simply to power cycle or netinstall a devices that was just working. In the past i have been requested to send in Sup Outs to support but the issue still exists even with recent ROS releases. My most recent freeze ups during upgrade are on these devices (these are from the past 7 days):
RB751U-2HnD, was at 6.2 , upgraded to 6.24 (reboot), no problem. then upgraded its FW from 3.07 to 3.18 (or whatever was latest FW as of 6.24), choose reboot, and the device never came back. this one required a netinstall.
RB 433- was at 6.13 upgraded to 6.24, reboot, device did not come back and had to be power cycled.
(4 other devices, mainly rb 433s upgraded to 6.24 with no issues)
this is purely anecdotal, but i feel like upgrading ROS in the past ( prior to ROS 6.x) did not cause any lockups or issues.