3rd tenancy agreement not honoured - guarantor on the hook?

Guarantor

I had a tenant walk half way through a 6 month AST this summer. This was the third tenancy agreeement. The earlier 2 were fine leaving no issues. The guarantee was put in place 3 years ago with the 1st tenancy agreement. I wrote to the guarantor saying all is well at the end of year 1 and the end of year 2. I have not yet sent the guarantor a copy of this 3rd tenancy which has gone wrong.

Does anyone know just cause or impediment in law as to why I cannot now send the guarantor a copy of this latest ast and then enforce it on them? Obviously I would go through the formality of a rent statement on the tenant first.