Backup script fails in 3.11

Why does the following script fail in 3.11, but works in previous versions? It increments and that’s about it:

/ tool e-mail 
set server=1.2.3.4 from="ME@SOMEDOMAIN" 

/system script add name=ebackup source={/system backup save name=([/system identity get name] . "-" . \
[:pick [/system clock get date] 7 11] . [:pick [/system clock get date] 0 3] . [:pick [/system clock get date] 4 6]); \
/tool e-mail send to="Me@SOMEDOMAIN" subject=([/system identity get name] . " Backup " . \
[/system clock get date]) file=([/system identity get name] . "-" . [:pick [/system clock get date] 7 11] . \
[:pick [/system clock get date] 0 3] . [:pick [/system clock get date] 4 6] . ".backup"); :delay 10; \
/file rem [/file find name=([/system identity get name] . "-" . [:pick [/system clock get date] 7 11] . \
[:pick [/system clock get date] 0 3] . [:pick [/system clock get date] 4 6] . ".backup")]; \
:log info ("System Backup emailed at " . [/sys cl get time] . " " . [/sys cl get date])}

/ system scheduler
add name="sched_backup_mail" on-event="ebackup" start-date=jan/01/1970 start-time=07:30:00 interval=7d \
comment="" disabled=no

It is bug introduced in v3.11, as far as I know it will be fixed in next version.