syntax errors in different lines since a few weeks

[Michelle Breitung]

since a few weeks i've errors i never had before. There were any kernel update with Mint Mate after 5.15.0-67 - but it is not working:

michelle@michelle-HP-255-G4-Notebook:~$ sudo update-grub
Sourcing file `/etc/default/grub'
Sourcing file `/etc/default/grub.d/50_linuxmint.cfg'
Sourcing file `/etc/default/grub.d/60_mint-theme.cfg'
Sourcing file `/etc/default/grub.d/init-select.cfg'
Generating grub configuration file ...
Found theme: /boot/grub/themes/linuxmint/theme.txt
Found linux image: /boot/vmlinuz-5.15.0-83-generic
Found initrd image: /boot/initrd.img-5.15.0-83-generic
Found linux image: /boot/vmlinuz-5.15.0-82-generic
Found initrd image: /boot/initrd.img-5.15.0-82-generic
Found linux image: /boot/vmlinuz-5.15.0-83-generic
Found initrd image: /boot/initrd.img-5.15.0-83-generic
Found linux image: /boot/vmlinuz-5.15.0-82-generic
Found initrd image: /boot/initrd.img-5.15.0-82-generic
Warning: os-prober will be executed to detect other bootable partitions.
Its output will be used to detect bootable binaries on them and create new boot entries.
Adding boot menu entry for UEFI Firmware Settings ...
Found memdisk: /boot/memdisk
Fehler: syntax error.
Fehler: Incorrect command.
Fehler: syntax error.
Syntaxfehler in Zeile 289
Syntax errors are detected in generated GRUB config file.
Ensure that there are no errors in /etc/default/grub
and /etc/grub.d/* files or please file a bug report with
/boot/grub/grub.cfg.new file attached.

the newer kernels i've installed with removing the /etc/grub.d/47_custom_proxy - if i remove it, the newer kernels will be installed.