I'm hosted on CloudWays

You should exclude cookies from varnish cache via the Cloudways platform. 

 Navigate to Application Management > Application Settings > Varnish Settings. 

 

 Add the following cookies in there 

 COOKIES 

 utm_campaign

utm_source

utm_term

utm_medium

utm_content

gclid

first_utm_campaign

first_utm_source

first_utm_term

first_utm_medium

first_utm_content

handl_original_ref

handl_landing_page

handl_ip

handl_ref

handl_url

organic_source

gaclientid

//and all the custom parameters created by you