Investigate why the Export button at LifterLMS > Reporting > Students is not working on a WPEngine website.

### Reproduction Steps
This only happens so far at HS-217775. This does not happen on my test site.

1. Deactivate all other plugins except LifterLMS 7.1.4.
2. Use a default theme (e.g., Twenty Twenty Three).
3. Go to `WordPress Dashboard > LifterLMS > Reporting > Students` and click on the `Export` button.
4. It will say `An error was encountered generating the export:`

### Expected Behavior
It must export a CSV file.

### Actual Behavior
It does not export a CSV file. It says "An error was encountered generating the export`"

### Error Messages / Logs
If you visit `WordPress Dashboard > LifterLMS > Statuys > Logs`, you'll notice that there are many notices in the debug.log file. The logs include `Your object cache implementation does not support flushing the in-memory runtime cache. Please see Debugging in WordPress for more information.` and other notices.

### This issue has be recreated:
+ [ ] Locally
+ [x] On a staging site
+ [ ] On a production website
+ [ ] With only LifterLMS and a default theme