X7-8 running RHEL 7.7 spontaneously executes sysrq reset

We have two X7-8 servers running Oracle "unbreakable" Linux 7.7.  These systems run our core application.  About once every month or two they spontaneously reboot.  Oracle support says the reboots are caused by a SysRq reset.  This can be caused by a process running as root executing "echo c > /proc/sysrq-trigger" or a particular key sequence on the server's keyboard or (I'm told) if the power button is held down.

The problem with these theories is that (a) the server is running headless (no keyboard), (b) the application runs as a service account without root access, and (c) the server is unattended in a locked cage in a remote colo.  So in order of suggested root causes, no part of the application runs as root, there's no keyboard attached, and nobody has physical access to the machine at the times when the sysrq occurs.