We have just release a minor bug fix on the nightly and stable build channels (v3.7 and 4.0) which fixes a bug in all file reader nodes when the file encoding ‘Guess’ option was selected in certain circumstances.
This patch fixes the error for all nodes showing the ‘Select file encoding’ option shown:
The original bug report and explanation of the problem is here:
Thanks to @Iris for bringing this to our attention.