Checklist before changing a shared login in your automations
I updated one saved login in n8n and two automations broke: my lead ads and my Instagram comment-to-DM, about 50 failed runs.
List everything that uses the login before touching it.
Know whether an update replaces or merges. In n8n, an update through the API replaces the whole login. Any field you leave out is wiped, and it still says success.
Send every field, every time. Get the full field list for that login type first.
You can't read a saved login back, so write down what's in it somewhere safe before you change it.
Re-test every workflow that uses it, not just the one you were fixing.
If a token works outside but fails inside, the tool probably isn't sending it at all.