The variable expansion does what it is intended to do. However this expansion is sometimes not compatible with the format of the exiv2 tag, in particular when its type is Rational or SRational.
I don’t see any simple solution for that. One possibility would be to create a specific variable for each problematic exiv2 tag. I’m not convinced this is desirable (case by case stuff, maintenance issue, …).
But I think your initial need may be satisfied. In fact you wanted to remove exif tags except some of them. For that we don’t need the variable expansion.
I’ll try to find a way to do it.
I suggest this the following. If you have disabled exif tags but you want to see some of them you enter the sign “=” in the formula.
