Starter motor problems

Hi all Td4 es manual
My problem is the starter motor is scrubbing against the flywheel teeth rather than engaging between them causing the start of rounding of the teeth edge. The flywheel and clutch was new on in march and was fine for about 3 months until the grinding started. I have tried another 2nd hand starter with the same results. I have also fitted it with the new plunger and contacts kit sourced from eBay. Ive also tried a new relay for the starter motor and made sure that the big wires are all tight with good connections. I'm reluctant to spend money on the car where possible as I want to sell it but Im out of ideas as to what would cause this. Also the battery from cold has 12.5 volts. The flywheel doesn't look that bad but if I have to replace it I want to find out why it's happened, anybody any ideas.

a lot of dust comes of these new style flywheels and can destroy the starter but as you have tried another it almost sounds as though your flywheel is loose

What other symptoms would a loose flywheel give? It drives ok but does rattle slightly when idling in neutral but my 12plate transit does that.