Maxscale Process was killed by rhel 7.5 due to high swap usage

We are using maxscale as a proxy to connect to mysql, most of the time it was observed maxscale is using high swap memory, in one situation it was noticed maxscale was killed by OS due to no swap space left.

Please can you tell us why swap memory of maxscale goes high, which is used only for proxy, no rules are used for filtering and other purpose. Just maxscale used as HA and proxy.