Due to regression in grub2 in RHEL 7.4 the search path for config file is incorrect. There is a workaround via regular expressions but due missing "insmod regexp" in PXEGrub2 template this does not work on RHEL. This ticket is a request to pull a template change into 1.15 series: https://github.com/theforeman/community-templates/pull/418

More info at:

https://bugzilla.redhat.com/show_bug.cgi?id=1370642#c70