[Decision/Grant] ForbiddenError: Unable to load OAuth 2.0 transactions about oauth2orize HOT 1 OPEN

I was getting the same error with my Zapier oauth integration.

I'd click Deny, then retry, then Deny or Accept, then it would fail and I'd see this in my server log:
{ ForbiddenError: Unable to load OAuth 2.0 transaction: lnfyhWk3

I found that it didn't fail if my browser cache was disabled, so I fixed it by turning off caching for my /oauth route in my Nginx configuration:

location /oauth/ {
proxy_pass http://blahblah;
proxy_http_version 1.1;
proxy_set_header Connection "";
proxy_set_header Host $host;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";

    # kill cache:  Fixed Zapier Oauth Deny, try again flow
    sendfile off;
    add_header Last-Modified $date_gmt;
    add_header Cache-Control 'no-store, no-cache, must-revalidate, proxy-revalidate, max-age=0';
    if_modified_since off;
    expires off;
    etag off;
    proxy_no_cache 1;
    proxy_cache_bypass 1;

from oauth2orize.