NTN part number is: NTN6001LLBC4/2A
Which is 28mm OD 12mm ID and 8mm thick.
RS shows the 6001-2RSH as being those dimensions but with a double rubber seal.
So you have the right one, or an equivalent.
From your photo it looks like you have installed it off center though, and so its fouling as the diagonal diameter is larger than it is when square.
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