This issue is caused by the avatar update algorithm here https://github.com/xwiki-contrib/ldap/blob/master/ldap-authenticator/src/main/java/org/xwiki/contrib/ldap/XWikiLDAPUtils.java#L1394 which:

• is deciding that the user avatar needs to be updated or not based on the current avatar vs the avatar from LDAP, but only based on the file name (not the format)
• then, in order to decide whether it needs to actually update the attachment (the image has changed on LDAP or not) it compares the bytes of the set avatar vs the new avatar - in this case it compares profile.png with profile.jpg, which are obviously different
  • however, when it updates it updates profile.jpeg
• then, after having updated the attachment it won't update the set avatar to profile.jpeg (because it had compared them to be the same, because it compares without extension)