Scorm Player:
We have just recently updated to version 2.5.3 and selected the Responsive Theme. We have noticed that on launching SCORM Activities that the SCORM player now loads the content and a page (rather than just the SCORM content) with navigation tabs forcing our content down the page effectively hiding our navigation buttons located at the bottom of the player window. When we switched back to the Standard Totara Theme the issue was resolved.
Audiences:
We have also had issues with 2.5.3 and the setting of audiences via Admin > Users > Audiences > Rule Sets. We found in when using the Responsive Theme the Approve Changes and Cancel Changes buttons were hiden from view. We resolved this by reverting back to Totara Standard Theme.