Companies under special administration attempt to collect money with any possible means, as this is the job of the special administrator. So this letter is sort of standard procedure and unrelated to whether the claim is justified or not. They offer discounts in the hope that a few of the probably thousands of clients rise to that bait.

In my opinion, most those claims are unjustified. Almost all brokers give the impression in their advertisements that clients are only liable for their deposit. Even if the fine print says otherwise, it is invalid for this reason under the jurisdiction of most countries. Of course this is just my personal opinion, no legal advice. I would react immediately and reject the claim in full in a brief letter.

There are many other reasons to dispute such claims, for instance the broker failed to explain in detail why he did not execute your close order, and failed to document his attempts to do so.

You'll need a lawyer only when they really file charges.