Please go to My Oracle Support certifications tab and make sure that both EBS 12.1.3 and database 188.8.131.52 are certified against Redhat 7.7.
Not only OS version, but kernel version matters.
Review the following document to check if there are additional steps required for EBS on RHEL 7https://support.oracle.com/epmos/faces/DocContentDisplay?id=761566.1
That's what I can think of. May be you'll get more suggestions