What do you mean by safety?
Perhaps you need to reword the request.

If you want to know how ACC insures that it's Assessors (Medical or otherwise) are fully qualified, and up to date - you should ask ACC about that specifically.

A responsible and accountable business in the rehabilitation field like ACC (which includes a lot of litigation) would reasonably be expected to have up to date records on the training, work history and continuing education of its various assessors - because that constitutes evidence of their expertise.

These people often have an intimate relationship with claimants (asking personal things about them and laying their hands on them).

The least ACC should do is to have a yearly updated curriculum vitae (including training, work history and continuing education) on assessors - and not wipe their hands of their responsibility.

The long term consequences of ACC using an assessor who is not expert or is suspect in some way is serious, not just in terms of ACC's accountability - but in terms of the consequences on individuals who might have been assessed by a person who is not the expert they claim to be, or otherwise has a dubious history that would make them inappropriate as an assessor.

Complaints about Assessors should be treated seriously by ACC. ACC should record and follow up every complaint - not just make routine excuses and fob claimants off. ACC should have a public record of complaints of all types (no names given). That way patterns are likely to become apparent - and problems can be identified and fixed rather than denied and perpetuated.