This article explains the meaning of below logs messages.

could not open file '/var/preserve/drain_config_latest': Resource temporarily unavailable load complete (1 errors)

Customer may get below error when trying to load update a config file as below.

user@labrouter# load update /var/preserve/drain_config_latest

error: could not open file '/var/preserve/drain_config_latest': Resource temporarily unavailable load complete (1 errors)

This error normally indicated issue with resource availability which can sometimes happen when box goes in hung state or some memory location error which make the memory unaccessible.

This can be recovered with the reboot of the box.