iOS and iPadOS mail shows only Chinese characters...

Every now and then I get an email on my 2018 iPhone X or my 2015 13" iPad Pro where the entire content is in Chinese characters.  However, when I look at that same email on my 2023 16" MacBook Pro (using macOS Mail), the email is just a normal email (plain English, no special characters, no emojis, no images).  The email also appears fine when I look at it in Gmail using any browser (Safari, Chrome).
When I look at the raw message on my MacBook Pro (Sonoma > Apple Mail > View > Message > Raw Source), there is nothing suspicious.
So this seems to be an issue related to the Mail app on iOS and iPadOS.  Does anyone know what the issue could be?