Okay... this is the same error that we encountered before... onto research!
Let's export the database from RHEL 6 again:
I ignored that warning before... but let's see if addressing the max_input_vars config solves the import issue on RHEL7?
Let's find where the php.ini file is located:
php -i | grep "Loaded Configuration File"
we will make a backup of the current one... call it php.ini.pre-rush-changes
now we can edit the php.ini without any worries 
— well.... but with caution:
Giving Apache the boot---
Let's do the same on RHEL7:
php -i | grep "Loaded Configuration File"
vim php.ini
It's commented; let's uncomment it and then give apache a boot.
Nope... still same error; I will revert the change in the php.ini file... as that had no impact it seems!