Seems like there's some error on Lemmy handling the picture:
{"error":"unknown","message":"Request error: error sending request for url (http://pictrs:8080/image/original/cfeaa87a-3aa2-4be2-ae19-335f36812014.png): error trying to connect: tcp connect error: Connection refused (os error 111)"}
Why not adding some conditional to enable it? Like fsck.rescue = $grub-error. If grub-error = yes, then fsck.rescue = yes too and then try again. If keeps failing then show the message. Otherwise it keeps being no and boot as usual.