Letter avatars missing after upgrade from v3.3.0.beta3 to v3.5.0.beta2

After a rebuild all of the letter avatars are missing from the forum. It looks like the relative paths have changed.For example, prior to the rebuild the letter ‘M’ had the base name 24.png, this has been changed to 72.png which is just an avatar placeholder. Is this a bug or expected behavior given the upgrade.

The rebuild is being run on a clone of the prod version of the forum. Initially issues were experienced with the rebuild timing out so a swap space was added, this seems to have allowed the update to run smoothly.

After rebuilding I have ran the command rebake avatars:refresh but this appears to have no impact on the letter avatars.

Solved I think, I had to disable this setting: