I would second the above recommendations RE: seeking guidance from your DCT and seeking further feedback on your interviewing performance. If you received 8 interviews in Phase I, it wound stand to reason that your application is competitive, at least in the context of passing the initial review stage.
What may have happened, and I apologize, as I don't know how to word this without perhaps sounding harsh, is that your application materials were competitive enough to secure interviews, but were still in the lower realm of all competitive applications. Thus, without a stellar interview, you were then ranked outside the top spots needed to secure a match. Looking at the match statistics, it does seem as though fewer people matched to their first choice and more people matched in spots 4+. This could then mean that sites had more competitive applicants per spot than in the past few years, and that more competitive applicants were applying to more sites, which would seem partly borne out by the fact that from the sites' side (and unlike for the applicants), the proportions of their 1st, 2nd, 3rd, etc., choice matches were similar to years past.
For PVMS, your best bet and the part over which you have the most control is to continue to hone your interview skills, since other factors (e.g., research, clinical hours) likely can't be addressed in the brief time available.
If you end up foregoing internship this year and apply again during your 5th year, multiple additional avenues for increasing your competitiveness are available. If you don't have many/any publications and posters, that would be my first recommendation, as that's the area that can often make an applicant stand out. Perhaps equally important would be defending your dissertation if you've not yet done that. More clinical hours are good, but after a certain point, there are rapidly diminishing returns.