None of our users are able to change their custom avatars following the last wpForo update. Under Settings>Features both Enable Avatars and Enable Custom Avatars are set to yes. The users have the selection to upload an avatar and can browse and select one, but after clicking Save Changes the old avatar remains. There is no error message and it indicates that the profile saved successfully. The avatar files I have used to test are below the maximum allowed file size and I have deleted the site cache.
This is either cache issue or file system permission issue, it doesn't allow to overwrite files or delete them. Or maybe you have a other plugin which sets all users avatar from own profile management page.
First please make sure wpForo forum page base URL is excluded from your cache plugin. All cache plugins have an option to exclude certain page. wpForo has built-in cache system it doesn't need to be cached from other plugins.
Then check file system, make sure all folders of these directory tree /wp-content/uploads/wpforo/avatars/ has 755 permission and all files in this directory have 644 permission.
Thank you, Robert.