SessionRotate() and StructAppend() not persisting across requests

In my Application.cfc::onSessionStart(), I copy old session data from a Mongo cache and then append it to the newly created session. Then I rotate the session since the client usually has old cfid cookies which I want refreshed.

The newly copied session data appears in the request since I dump the session in OnRequestStart(). However, on the next request, it creates a new session even though the next request had the same cfid cookies it got from onSessionStart(). I changed this unworking code:

... //cacheGet() etc...
structAppend(session, local.sessionScope, true);                            

// If I sessionRotate(), then I must recopy local.sessionScope over...   
// NO: this still does not work! structAppend(session, local.sessionScope, true);

to manually copy the variables between my old session struct with the new, actual session struct, and it works across any series of requests:

... //cacheGet() etc...
for (k in local.sessionScope) {
    session[k] = local.sessionScope[k];

Is there something different about how structAppend() interacts with the in-built session scope??

OS: Linux
Java Version: Oracle JDK 11.07
Tomcat Version: 9.0.35
Lucee Version: Lucee

you not overwriting the new cfid from sessionRotate() with the older cfid values from the local.sessionScope when you update the session scope?

are you seeing Set-Cookie headers being set?