Wirquin Twisto shower waste?

Twice in three years the rubber seal on the Wirqin Twisto waste on my shower tray has parted with disastrous flooding. The first time this happened I replaced the whole unit but it has just happened again. The problem is due to bad design of the seal which is a strip curved round and glued at the ends to make a ring. The joint in the ring gives way after 18 months or so. Ideally the seal should be made from a continuous ring. Any ideas how I can prevent this happening again? Replace the seal with two suitable sized 'O' rings perhaps?