You don’t need any ReWrite Conditions? Usually I’m accustomed to seeing something like this (this is purely a random example)
{REQUEST_URI} ^/api/v1/websocket [NC,OR]
RewriteCond %{HTTP:UPGRADE} ^WebSocket$ [NC,OR]
RewriteCond %{HTTP:CONNECTION} ^Upgrade$ [NC]
RewriteRule .* ws://127.0.0.1:8065%{REQUEST_URI}