I upgraded to Jenkins 2.19.1 yesterday and with it the email-ext plugin to v2.52.

(It is possible that this is an issue with the description-setter plugin. However, it shows now updates since 2015 and I believe I was already using its latest revision. Correct me if this belongs with that plugin.)

I have been using the description-setter plugin's token: DESCRIPTION_SETTER_DESCRIPTION to populate the the email subject line.
$DEFAULT_SUBJECT - ${DESCRIPTION_SETTER_DESCRIPTION}

Following yesterday's upgrade to v2.52, I no longer get the value of DESCRIPTION_SETTER_DESCRIPTION, in the email subject. I get the raw token name instead.