Querybuilder returns incorrect results occasionally

I'm having an issue where the querybuilder will occasionally return incorrect results. I have a requirement to add a label to collections containing assets with a restricted tag. It works most of the time, but occasionally the querybuilder will return collections that don't contain any restricted assets.I have a clientlib that grabs all the collection paths in the viewport and sends it to the servlet that runs the query. Based on my logging, it appears that the error is occuring in the servlet when it receives incorrect results showing a collection has an asset with the restricted tag, but doesn't. There doesn't seem to be any consistency with which collections/assets this happens to.  I have tried running the queries through the debugger repeatedly to see if it would return incorrect results, but I haven't been able to reproduce the error there. Any idea why this would happen? I'm running aem 6.5.

@Component(service= Servlet.class,
        property={
                Constants.SERVICE_DESCRIPTION + "=Check collection restrictions.",
                "sling.servlet.methods=" + HttpConstants.METHOD_POST,
                "sling.servlet.paths="+"/bin/my/check-restrictions"
        })
public class CollectionRestrictionServlet extends SlingAllMethodsServlet {

        private transient Logger logger = LoggerFactory.getLogger(CollectionRestrictionServlet.class);
        transient Map<String, String> querymap = new HashMap<>();

        @Reference
        transient QueryBuilder queryBuilder;

        @Override
        protected void doPost(SlingHttpServletRequest request, SlingHttpServletResponse response)
                throws IOException {
                try {
                        Session session = request.getResourceResolver().adaptTo(Session.class);
                        RequestParameter[] param = request.getRequestParameters("item");
                        List<String> collections = new ArrayList<>();
                        List<String> resCollections = new ArrayList<>();
                        for(RequestParameter par : param){
                                collections.add(URLDecoder.decode(par.getString(), "UTF-8"));
                        }
                        Writer writer = response.getWriter();
                        logger.info("Collections checked for asset restrictions: " + collections);
                        for(String col : collections){
                                querymap.put("path", "/content");
                                querymap.put("type", "dam:Asset");
                                querymap.put("memberOf", col);
                                querymap.put("property", "jcr:content/metadata/restricted");
                                querymap.put("property.1_value", "my-asset-info:restricted/do-not-modify");
                                querymap.put("property.2_value", "my-asset-info:restricted/credit-to-photographer");
                                querymap.put("property.3_value", "my-asset-info:restricted/credit-to-designer");
                                querymap.put("property.4_value", "my-asset-info:restricted/digital-use-only");
                                querymap.put("property.5_value", "my-asset-info:restricted/social-media-use-only");
                                querymap.put("p.limit", "1");
                                Query query = queryBuilder.createQuery(PredicateGroup.create(querymap), session);
                                SearchResult result = query.getResult();
                                long resNum = result.getTotalMatches();
                                logger.info("Collection: " + col + " returned " + resNum);
                                if (resNum > 0){
                                        resCollections.add(col);
                                }
                        }
                        if (resCollections.size() > 0){
                                String out = resCollections.toString();
                                logger.info("Collections with restrictions sent to clientlib: " + out);
                                writer.write(out);
                        }
                        else {
                                writer.write("");
                        }
                }
                catch(Exception e){
                         logger.error("Unable to obtain asset restrictions for collection " + e);
                }
                }
}