SNAT Translation List utility config

Hello everyone,

Yesterday I encountered a case like this:
I created Local Traffice -->'SNAT translation list', before creating SNAT list and SNAT POOL, after creating, some traffic of VS had 504 gateway error, however, the IP and vlan of VS is 172.31.33.0/24 while the SNAT traslation I created has IP 172.31.22.20-22. But right after I deleted SNAT, the traffic returned to normal.

In conclusion, everyone, let me ask if creating 'SNAT Translation List" before creating SNAT and SNAT Pool has any effect.
Sincerely thank you,