Problem when using dmx-on:add in Tagify

4.8.2

I want to change the query parameter when some tag is selected or removed in Tagify input.

But it works strangely for dmx-on:add.

I started with empty input.
Then I select a tag with id 1.
I see that the corresponding query param appears, but it is empty. For example, it is &user=.

Next I add one more tag, with id 2.
And parameter changes to &user=1.

Next I add third tag, with id 3.
Parameter changes to &user=1%2C2.
etc

It looks like it is setting the value to query before adding, not after.

(Removing seems working fine)