I took a look at commit 6d0c77edac6cf78e2fbe6e71e64836a51fb40623 and I don't think it is relevant here, as it deals with ubuntu version upgrades between packages which were never in debian I am thinking to fix this bug by adding a pre.inst to xmame-x and xmame-sdl/0.146-2. which would remove the symbolic link on upgrade