Hello Tom,
thx for your reply.
Bloom wasn't of much help here, to my surprise I must say. Before it showed an effect on the bright spots the rest of the image vanished in a veil of light.
The sun was already at 5, going up to 20 finally actually helped, but made the scene shadows even softer, of course.
The glossiness I had to increase to 0.99 to get some effect.
To my surprise, too, the denoiser did not have any impact on that area.
So, in the end, just getting rid of too much bump was the only solution (the one I had already used in the actual image).
I had hoped for some magic setting in the render settings I had missed, but obviously the bump value was the critical one here (i had not even seen 25% as "very much", but I was wrong) and the only one that mattered.
Thx again for looking into my testcase,
Michael