One way I found to reproduce this:
- Have some pair of languages, say en->sr
- Change target language to en. Automatic swap will give sr->en pair
- While suggestions are loading (you don't even need to be that fast) change target language back to sr. Swapping will make the pair be en->sr.
So, while one request is pending, triggering another will give double results. List of Suggested pages (list below "For later" list) is also doubled.