Event Fees not loading when registering in back-end
This is a core bug, I have created issue for this bug at https://lab.civicrm.org/dev/core/issues/189

I have submitted a fix for this at https://github.com/civicrm/civicrm-core/pull/12333 . Can you please QA by applying the patch manually to your instance? 

Please comment your QA result on PR so that it will helpful to get merge quickly.

Thanks

Pradeep