@jnissen: here is the link to a recent reply on a different thread, which included instructions on how to do OTA update:
https://opensprinkler.com/forums/topic/os3-reboots-randomly-and-eventually-view-logs-fails-and-reboots/#post-48937
@Pete: it’s the .bin file in the folder that you should upload. You can use OTA update as the link above explains.