Probably totally unrelated to your issue, initially on reading your thread I thought pads moving in brake caliper, however.Check you don’t have play in the rack itself. I had a knock I couldn’t find on my 100hp. It wasn’t until I was trying to tighten up a new inner tie rod that I noticed there was a load of play in the rack itself.
The original poster reported back the correct solution in AugustI spanner-checked everything a few weeks ago an now the knock has gone!
I nipped up everything but I think it was the bottom caliper carrier bolt as that felt slightly loose!
Thanks for you everyone's help.