Reverse Proxy Not Behaving

Seems that the obvious difference is that /moodle maps "cleanly" from: from URL to moodle's location where /lrs-dashboard does not:

http://example.com/moodle -> http://a.b.c.d:8080/moodle

http://example.com/lrs-dashboard -> http://a.b.c.d:3000

That being the case, what about that would cause the reverse proxy from behaving as I would have expected?