Boxes - How to Correct Broken Encoding
1. Remove UTF-8 Control Characters
If you data contains UTF-8 control characters that cause issues when downloading the final feed, use the box "Remove UTF-8 Control Characters".

2. Preg Replace
Your feed can contain broken encoding, that the platform shows you with bold text like this: <c2 8b> or <c2 92>
As this is no 'real' text, it can't be replaced with a "Text Replace"-Box, but requires a "Preg Replace". Just insert the box as shown below and the tags will disappear:

Here you can copy the Regular Expression: /[\x{0080}-\x{009F}]+/u