I’m having the same problem with what I think is the same line of code (#188) in the _functions.php file.
In my case, the backslashes get stripped from plain text fields where I need to store regular expressions.
Your suggestion about hooking to the ‘update_field’ filter won’t work because you are calling streepslashes_deep() BEFORE the apply_filters() call.
I think the option of the backend filter is a quick one, but it may also be useful to pass more info to the filter, e.g., the field type and name, field group, etc., so the programmer can have more context info in order to make the decision either to return false or true.
Thanks in advance,
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