Was suffering from this issue in previous version of Catalina and now in Ventura latest Mac OS still not resolved . Only subject could be seen, no body message has been loaded. Funky thing is some threads there are some not or some are showing but then when you scroll down the body message disappears....
MacBook Pro 13″, macOS 13.2
Do you have any add-ons or plugins installed for the Mail App?
Any 3rd party utilities or Anti-Virus apps installed on the Macbook?
Does this happen in Safemode?
Start up your Mac in safe mode - Apple Support
Thanks it does too. I have Surge installed as VPN, that's the only one I could think of. No add-ons or plugins.
Gone through 2 months of back and forth with Apple CS and they confirmed it is an engineering issue but no fixes for 2 versions of Ventura already so hoping to see if could escalate here to get a resolution for this bugging issue. Even sent in logs via their Capture Data app.
Mac Mail Preview Pane Body Message Still couldn't display/will disappear when scrolling at times
