I will try to be fair with my input. I know that many people are very loyal to their SXM car rental company, as am I. More than 20 years ago I did have a problem with Hertz that the local management chose to ignore. It was at this time that I learned that SXM local franchisee did not have support of parent company as you have already stated. I eventually received reimbursement from Hertz, USA only as an accommodation and concern for their brand name reputation.
That was a long time ago and I am sure lots of changes have been made, but it does pay to do appropriate research prior to making any decision.