Ask HN: What might be causing this Gmail error?

My spouse seemed to have just run into a version of the error described at https://support.google.com/mail/thread/8328266/phone-shows-a-different-sent-email-than-my-computer?hl=en

Unlike the OP, she did all of the drafting (i.e. draft 1 and draft 2) and sending from her laptop Chrome. The sent email on laptop Chrome looks like draft 2. The sent email that she sees on her mobile gmail app looks like draft 1.

I had her forward me the sent email from laptop Chrome and from the mobile gmail app. The forwarded emails I received from each device were, in fact, different.

Is this a caching issue? Why is that forwarding from each device will persist the difference? Is it possible to tell from the headers which one is the "original" / "correct" / ???.