Possible RegEx bug for lower-case a and s characters

We observed that when we used this RegEx expression: [\s+|"]|[\n\r\f\a\t]|[^[:ascii:]]

The lowercase letters “a”, and “s” were also stripped from our data columns.

The RegEx expression seems to be error free as described here:

Sample SQL to test:

select regexp_replace('Nigel DeFreit a  s', E'[\s+|"]|[\n\r\f\a\t]|[^[:ascii:]]','','g') AS result;