StringReplacer behaves differently on different columns

Hello,

The following settings of the StringReplacer works for some feature attributes, and doesn't work for others.

This is aimed to replace dots for commas (or vice-versa) in a decimal number.

So, it normally works for example like 100.5 -> 100,5

But, I just used the very same transformer in a different feature, and the result is zero, for example: 100.5 -> 0

Both columns are 64-bit real. I can see in the the "cached features" in Data Inspector that a valid decimal number goes in, and out goes the zero.

Any ideas?

Thanks in advance