https://issuetracker.unity3d.com/issues/argumentoutofrangeexception-error-is-thrown-when-element-is-deleted-in-the-propertydrawer-listview https://forum.unity.com/threads/listview-remove-button-in-footer-serialized-property-disappears.1207432/ Unity issue, I can't seem to find a workaround. May just have to wait for Unity to fix. It's a minor issue as it just throws errors.