1530H Mulching Kit

[alfapat]

Recently acquired a 2021 1530H with a mulching kit fitted . After 4 05 changes to different lawns involving taking out and putting in the mulching plug , it blades on start up destroyed the plug !

All I have discovere is after purchasing a new plug and inserting it It wouldnt drop in were it should , so it was catching the rear top edge of the shoot nearest the blade. There is a bracket clamped on the raise and lowering bar bolted to the bar under the deck cover between the foot steps . This bracket sits on the shoot when the deck is in the raised position and it may have revolved round from its original setting (put in there by the machinery supplier prior to me buying), So I slackened it and turned it towards the shoot for extra pressure.
The plug now goes in rather awkardly but still doesnt explain why the blades made contact and destroyed the original one .
Has anyone got some knowledge of this please?