Explain Google Tag Manager issue

[Maxim-Mazurok]

I was getting this from users:

{
  "blocked-uri": "https://www.googletagmanager.com/gtag/js?id=G-EVQQLXSL5E",
  "disposition": "enforce",
  "document-uri": "https://app.borderwise.com/sw.js",
  "effective-directive": "connect-src",
  "violated-directive": "connect-src",
  "original-policy": "default-src  'self'; frame-ancestors  'self'; style-src   'self' 'unsafe-inline' https://fonts.googleapis.com 'unsafe-inline'; script-src-elem  'self' https://*.googletagmanager.com https://*.hotjar.com; style-src-elem  'self' 'unsafe-inline' https://fonts.googleapis.com; font-src  'self' https://fonts.gstatic.com https://fonts.gstatic.cn; connect-src  'self' https://localhost:33443 https://localhost:43443 https://*.ingest.sentry.io https://*.hotjar.com https://*.hotjar.io wss://*.hotjar.com https://*.google-analytics.com https://*.analytics.google.com https://*.googletagmanager.com  'self' https://fonts.gstatic.com https://fonts.gstatic.cn  'self' https://*.google-analytics.com https://*.googletagmanager.com  'self' 'unsafe-inline' https://fonts.googleapis.com; img-src  'self' https://*.google-analytics.com https://*.googletagmanager.com; report-uri  /api/v1/reports/csp-report;",
  "status-code": "0",
  "referrer": "",
  "script-sample": ""
}

Basically, it's blocking GTM even thought it's clearly allowed.

I assumed it was due to some ads/privacy plugins, but couldn't reproduce, because in my Chrome, Ublock Origin would use 307 internal redirect, see https://stackoverflow.com/a/27948729/4536543 like so:

However when I got the same error from one of our devs, we looked more into it, he was getting stable repro in his Chrome with same plugin with same settings. I tried same plugin with same settings in Chromium (as opposed to Chrome) and it reproduced.

I don't know what A/B experiment my Chrome was part of, but yeah, now it's solved.

Reporting this in the issue for now, will create PR to close this issue when I get a chance. Hope this helps someone, cheers!