I am sorry to hear of the problems you are experiencing.
You need to check if the problem is in the removable cassette or in the system itself.
To see if the problem is in the cassette, remove it from its housing.
Then get a small magnet, and hold it against the small reed switch in the now empty housing (the one with the wires on it near the fuse), and have someone inside to see if the 'full' light comes on. If it does, then the problem is inside the cassette. It uses a small float, that has a permanent magnet attached. As mentioned above, you will need to see that the float lever is moving freely, and if necessary, replace the magnet.
(The reed switch is comprised of metal contacts, that come together when a magnet comes near them)
To see if the problem is in the cassette, remove it from its housing.
Then get a small magnet, and hold it against the small reed switch in the now empty housing (the one with the wires on it near the fuse), and have someone inside to see if the 'full' light comes on. If it does, then the problem is inside the cassette. It uses a small float, that has a permanent magnet attached. As mentioned above, you will need to see that the float lever is moving freely, and if necessary, replace the magnet.
(The reed switch is comprised of metal contacts, that come together when a magnet comes near them)
I hope this assists you in rectifying your issue.
We always suggest you to get in contact with your dealer or one of our Service Centres to ensure a correct and safe resolution to your problem.