Turning off “processing order” e-mail breaks checkout

This is a dev site. I’m currently using check or (test) stripe when processing. Both go to “on hold” (I am using auth but not capture in my stripe settings.)

I don’t want an extra e-mail sent when it changes to “processing.” As such, I went into woocommerce>settings>emails. Then I clicked on “manage” for the processing e-mail. I unchecked the box for “enable…”

Now, when I complete checkout, it still goes to the correct URL, something like:
https://budgetdiscmakers.com/checkout/order-received/3216/?key=wc_order_SnUer8z5JYCGw

except it gives a 404 error (goes to my default page not found page)

When I turn this notification back on, the problem goes away. This is really weird, since:
1. Orders don’t go to “processing” initially
2. This shouldn’t even happen if I AM going to “processing”

I just upgraded to the latest woocommerce. I don’t know if this was a problem before or not, because I previously had not turned off this e-mail.

The page I need help with: [log in to see the link]