Blair,

I'd say someone has used a cleaner (petroleum based) which has reacted with the clear.  I don't know how thick the D.E's are cleared.

I would think a decent cutting agent may take it off, other than a wet sand 1500 grit then polish / buff.

Might be a bit too much for a TC kit, not sure.

Eitherway I would suggest a full strip of the playfield is in order.  Worst case if it needs to be sanded out, a GNR is worth re-clearing the playfield.

Agree with this... id be looking at trying to cut back with a cutting compound... tamiya make a course and smooth compound, but its in small tubes. Hopefully the damage is all surface and not eaten into the CC. Id be doing a test area with a cloth and fingertip... good luck