The code you suggested above doesn't work - the #REF! errors remain in the code and it appears to skip over replacing them. My original code did work - it was just super slow, I suspect because of the the 'For each calc' part.
Your code returns an error 'No cells were found' despite there clearly being #REF! errors in cells. I suspect however even if your code were to run, it would actually wipe the formula from the cell? I wish to retain the formulas, just remove the #REF! error inside it.
I was thinking something like the below would work however I still get the same error of 'No cells were found' if I try to replace all 4 lines of original code. It's almost as if it's not searching the formulas within the range properly.