Whenever starting a RA Web Service REST job after an upgrade to 21.0, starting a job kills the agent.
Restarting the agent kills the job (ended not ok) or leaves it in Waiting for host and puts the agent into ENDED_LOST - ended undefined (host terminated prematurely).
RA WebService REST Agent solution: 4.6.0
RA Core version: 12.2
Using a 12.2 RA Core agent against a 21.0 system
There are two parts to RA agents, the solution (which is loaded into the database) and the core which is the process that actually runs on the OS. This issue is caused by the core being outdated.
Upgrade the RA Core by going to https://downloads.automic.com/downloads/advanced_mode and choosing "Automation Engine" as the component, 21.0 as the version (this will also apply to later major versions as they are available), and choose "Agent RA Core" as the Sub-Component. Download the correct .zip file for the agent install it.