I've been experiencing an issue with my Caroma Dual Flush toilet recently where water is spraying up on the tank lid and leaking down the side of my toilet when I flush it. After some googling I came to the conclusion that it was an issue with the fill valve washer.
I purchased a replacement washer (I believe it was this one https://www.bunnings.com.au/kinetic-40mm-caroma-no-2-ballcock-washer_p4920276) which has a diameter very slightly less then the worn one however I assumed this was due to the old one having stretched out over years of use.

I replaced the washer and the spraying issue stopped but a new issue presented itself. The tank would never stop filling. At the time I switched back to the old washer and just flipped it upside down which fixed the issue temporarily however today the tank spraying issue has resurfaced and i'd like to find a permanent solution.
Any advice would be much appreciated