Insurance company NCB problems?

Anyone ever heard of insurance company asking for original proof of NCB on a previous cancelled policy in addition to the current NCB when renewing with a new company?

I had a previous policy which was cancelled following a 6 month driving ban. Renewed with original company for one whole year following ban. Sent proof of full bonus from this year to new company. Now new company are saying they also want original cancelled policy proof of bonus (from 18 months ago). In effect they want me to provide them with 2 NCBs

My current insurers are saying by law they cannot issue 2 NCBs and are refusing to provide any other letter with such details.

Any ideas what on earth is going on here. Perhaps someone in the insurance industry can shed light on this. My ban has been fully disclosed to new company who would be cheaper for the renewal if I could provide details required.

I cannot figure out their reasoning on this. I already have normal proof of bonus which they wont accept.

Answers:
Sorry must be an out of state thing. Never heard of something like that in CA
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