I noticed this for a while, but not currently a problem on iOS 12.2. Weirdly it only seemed to happen on the London Review sub-forum for me, worked fine on General and London - General Discussion
My workaround whilst I had the problem was to long click on the link I wanted, which prompted to open the wrong link in a new tab / window, cancel that and clicking worked fine after that, but came back if I refreshed the London Review sub