According to my log, it seems the Range in my ontology is not a valid SL Axiom, even though ObjectPropertyRanges are accepted in OWL EL, QL, and RL. This is causing issues with SL reasoning, like taking 20 minutes for a reasoning query to complete or not returning the proper results.
The "Not a valid SL Axiom" warnings are on lines 22066 - 22070 in the log.