If you have one of the new wheeled cassettes do NOT use the wheels on anything abrasive such as concrete or tarmac. The reson is that the wheels will wear (even a small amount)then the cassette will not go into the housing properly
is it safe to assume this a toilet cassette? if so i'm ok i'm still in the old days of carry out
Yes it is the new toilet cassettes that have this problem. Like yourself i still have the old carry type but know of this problem as I work in the trade