Strange behavior with routes between master / slaves

Hi there!
I have maxscale 2.1.3 and 3 percona56 servers with master/slave replica. When i connect to my maxscale and make a sql select request - i see strange behavior from my maxscale.
For example, if i make

SELECT @@server_id

maxscale ALWAYS return 13 - this is id of my percona slave server - that's ok, all correct.
BUT if i make any request with

REGEXP SELECT her FROM (SELECT @@server_id as her) as t WHERE her REGEXP '.*'

i ALWAYS get 12 - this is my master ID.
In other words, SQL REGEXP in my any requests affecting routes between slaves and master. Why this happens? How to avoid this?