Issue
I've mapped a custom object and I'm updating its Name field in my Postgres database. When the record gets synced to Salesforce, the Name is showing up as an ID (e.g. a07EE000027APMyYAO) instead of the name I used.
Resolution
This can happen if you've recently changed the type of the Name field from a type that gets created automatically to one that isn't. For example, you could have changed the Name field from an Auto Number field to a Text field.
When you make a change like this, you need to view the details of the mapping in the Heroku Connect dashboard. That will force Heroku Connect to refresh its information about the mapping -- it will know that the Name field can now be written to.
The reason for the Name getting the ID value is that Heroku Connect was ignoring the value you used (because it still had the old information about the field being an Auto Number field). When custom object records get created in Salesforce without a Name, the ID is used.