We found a major issue using the transformer plugin module type. This issue blocks us releasing our Scroll Wiki Exporter plugins and may also influence plugins of other providers.

In com.atlassian.confluence.content.render.xhtml.PluggableTransformerChain a PriorityQueue is used to sort weighted transformers. Later an iterator is used to execute each of them. Our problem is that iterating a PriorityQueue does not guarantee the ordering. Please refer to PriorityQueue documentation

The Iterator provided in method iterator() is not guaranteed to traverse the elements of the priority queue in any particular order. If you need ordered traversal, consider usingArrays.sort(pq.toArray()).