478 memory saves failed because one leftover line at the bottom of a settings file overrode the correct setting above it. When a change doesn't seem to take effect, run through this.
Search the whole file for the setting's name. In most settings files the last copy wins.
Check every place settings can come from: the file, environment variables, and any per-user or per-profile copy.
Restart the thing that reads it. Many apps only read settings at startup.
Test the actual behavior, not the file. Make one request and check the log shows the new value in use.
Look for silent failures. A queue of failed jobs, retries or timeouts often means it's still using the old value.
After fixing, retry what failed. The saves that failed while it was broken don't retry themselves.
What it cost me
Every save waited on an old local model that kept timing out, and that model held 43 GB of my Mac's memory the whole time.