Okay! That seemed to fix it! Thank you so much for the help.
I’ve decided to change my plan a bit from rewriting to just permanent redirecting, so here’s the final relevant section of my nginx config if anyone else runs into this:
location / {
proxy_pass http://site.com:8088;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
rewrite ^/dashboards$ /data/perspective/client/DashboardProject permanent;
}