SSO OAuth2 proxy errors

We're using an on premise installation of Retool and are seeing some intermittent issues with Google SSO login. This is particularly the case for newly invited users, and one of our user accounts in particular.

Scouring the logs, we're seeing an oauth2sso/login proxy error occurring around that time that I feel is the likely culprit:

2021-11-11T07:47:01.216+11:00

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[HPM] Error occurred while trying to proxy request /oauth2sso/login from site.name.redacted to http://localhost:3001 (ECONNRESET) (https://nodejs.org/api/errors.html#errors_common_system_errors)
[HPM] Error occurred while trying to proxy request /oauth2sso/login from site.name.redacted to http://localhost:3001 (ECONNRESET) (https://nodejs.org/api/errors.html#errors_common_system_errors)

We're hosting this on ECS, and it works perfectly for some users but not others.

Any information on what this error may be indicating, how to resolve or work around it would be most appreciated, as this is blocking progress for us at the moment.

Env vars set that may be pertinent to help diagnose:

TRIGGER_OAUTH_2_SSO_LOGIN_AUTOMATICALLY : true
DISABLE_USER_PASS_LOGIN: true