PC_LOAD_A4 just isn't confusing enough.
LOAD_A4_PAPER or INSERT_A4_PAPER etc also fit within the limited length of the message.
I have done a stint of helpdesk work and can’t see that this would be too catastrophic.
Yes, it'd cause the person to check every tray, but in my experience they do anyway.
PC_LOAD_A4 just isn't confusing enough.
LOAD_A4_PAPER or INSERT_A4_PAPER etc also fit within the limited length of the message.