User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:90.0) Gecko/20100101 Firefox/90.0

Steps to reproduce:

1. Enable Enhanced Tracking Protention
2. Visit officeworks.com.au
3. Add an item to your shopping cart
4. Click "View Cart & Checkout" (https://www.officeworks.com.au/app/checkout/)

Actual results:

The page reports "Something went wrong. An unexpected error occurred. Click here to reload the page."

In the JavaScript console, I get:

TypeError: t.R3_COMMON.setRegionId is not a function
    e web_components_ReviewYourItems-web_views_Confirmation.dc463b32dc895eaed18d.bundle.js:660
    e web_components_ReviewYourItems-web_views_Confirmation.dc463b32dc895eaed18d.bundle.js:675
    e web_components_ReviewYourItems-web_views_Confirmation.dc463b32dc895eaed18d.bundle.js:741
    e web_components_ReviewYourItems.4f8683a9c1e1c6291f42.bundle.js:1
    Ku vendors-client.808d0f78ba779f168510.bundle.js:2
    unstable_runWithPriority vendors-client.808d0f78ba779f168510.bundle.js:2
    lo vendors-client.808d0f78ba779f168510.bundle.js:2
    $u vendors-client.808d0f78ba779f168510.bundle.js:2
    Ru vendors-client.808d0f78ba779f168510.bundle.js:2
    ho vendors-client.808d0f78ba779f168510.bundle.js:2
    unstable_runWithPriority vendors-client.808d0f78ba779f168510.bundle.js:2
    lo vendors-client.808d0f78ba779f168510.bundle.js:2
    ho vendors-client.808d0f78ba779f168510.bundle.js:2
    po vendors-client.808d0f78ba779f168510.bundle.js:2
    Pu vendors-client.808d0f78ba779f168510.bundle.js:2
    enqueueSetState vendors-client.808d0f78ba779f168510.bundle.js:2
    setState vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    r vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    r vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    r vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    r vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    r vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    r vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    r vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    r vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    r vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    r vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    r vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    r vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    v vendors-client.808d0f78ba779f168510.bundle.js:2
    e client.c4062553630661f45ea6.bundle.js:1
    e client.c4062553630661f45ea6.bundle.js:1
    Lr client.c4062553630661f45ea6.bundle.js:1
    O vendors-client.808d0f78ba779f168510.bundle.js:2
    n vendors-client.808d0f78ba779f168510.bundle.js:2
    r vendors-client.808d0f78ba779f168510.bundle.js:2
    c simple-header-857f67481045a19ed273.js:22
    _invoke simple-header-857f67481045a19ed273.js:22
    t simple-header-857f67481045a19ed273.js:22
    n vendors-client.808d0f78ba779f168510.bundle.js:2
    i vendors-client.808d0f78ba779f168510.bundle.js:2
    i vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    e vendors-client.808d0f78ba779f168510.bundle.js:2
    ie client.c4062553630661f45ea6.bundle.js:1
vendors-client.808d0f78ba779f168510.bundle.js:2:1042284

Expected results:

I should see the contents of my shopping cart.

I was able to complete the check-out flow by adding a breakpoint at the offending function call, and then running:

t.R3_COMMON.addSegment = function() {}
t.R3_COMMON.setRegionId = function() {}

...however it looks like this might already be solved in Firefox 91 by Bug 1713725.

Yes. this does essentially look like a dupe of bug 1713725.