This fix worked for me without needing to revert back to a previous save. I did not get any cutscene but got the “All that Glisters” main quest as soon as my game was loaded.
Worked for me too. Just talked to Radzig in Rattay, then traveled to the campsite (during day) and instantly got the cut-scene, making it possible to advance further.
Same issue with no cut scene, reloaded to right before I brewed the potion, cured the villagers, sent the Cuman to Rattay jail. Immediately reported to Sir Radzig and the cut scene finally started.
still does not work as I write these lines (1.3.3). If you have already validated your quest “Pestilance” and then validated the quest “Questions and Answers”, you are still stuck on this quest with the objective of finding the merchant who provides the money and the material. Lord Radzig offers no other dialogue and this simply does not unblock the situation. I begin to despair … for my part I think I will not go further. The bugs on major quests preventing to play a game that costs not less than 60 euros, in 2018, this is amateurism and an inability to work properly.
What worked for me was making sure the pestilence quest was finished, and no longer active in the quest log. That means waiting a few days for the cure to kick in at Merhojed, so that a new dialog option appears when speaking to Melichar. This completes the quest, and if I then go to see Sir Radzig the cutscene does start after our conversation and all is well.