On the 159/Brera you held the manual fold button until it beeped.

 

It’s on the infotainment menu on the Giulia but won’t stay set to on

 

according to MES, on older infotainment firmware, you can only force it via proxy alignment:

This function can enable/disable the menu for automatic folding of the side mirrors. The menu does not work/appear on models with old multimedia systems,
but auto-folding on these cars should be disabled when you set this option to "Present".
To enable or disable this functionality you need to execute this adjustment and select enable or disable.
PLEASE NOTE: You have to execute the PROXI Alignment procedure after changing this value! Otherwise your vehicle will not accept the changes.

 

Not sure I understand, you're talking about enabling it through MES, it was already enabled from factory but stopped working (set to ON but defaults to OFF), I disabled on MES then reactivated but still defaults to OFF

 

Do you have any idea what might have changed at the point it stopped working? I assume it had been working fine up until then? Was anything else changed or fitted or updated? Had you done anything with MES around the time you noticed they weren't folding in after locking?

 

Do you have any idea what…

Only things were Alarm sensitivity (main reason for MES in the first place) and Auto High Beam

Don’t see how either of those would affect auto fold

 

No. I agree. I haven't adjusted the alarm on mine but I also enabled the auto high beam and my mirrors are fine. Could it be something to do with an infotainment update? I'm just guessing tbh. Yours is gen 1 but it was fine so I don't get it really.