Please try it without the * in front of .flacf and without the ending *
You have to use the exact string you want to replace, without any wildcards.
And please don't replace it with a invisible character like a space.
A space is not "nothing" - it is just no more visible but still there.
If you replace your unwanted string with a space, you get this example result: 1981-03-14__-_San Diego (UAG)
The underscores just represent the number of spaces.
Has this resolved the problem so that all the original files have been modified?
If not, then it would be nice to see the data from a file before the action has been executed.
The reason behind it:
It does not look plausible to me that a field is referenced that does not exist, here the field with the trailing space in the name.
So, my suspicion is: both fields existed before the action was executed but only the "normal" field without the trailing space in the name was displayed while the action dealt with the field with the trailing space in the field name.
I doubt that a replace action leads to a duplication of fields that in the end have a similar name.