Contract clause on counterclaims

Good evening,

I have a question regarding a contractual component of our work contract.
There is the clause:
"The client can only offset against undisputed or legally established counterclaims."

From this, I understand that in the case of defects, the legal route is generally the only option for me.
So it is not sufficient to have them determined and recorded by a building surveyor?

Is this a common clause?
How can it be better defined in our favor?

Honestly... I had to google that out of curiosity.
Now it gets exciting!

BGH, judgment of 07.04.2011, file no. VII ZR 209/07
§ 9 para. 1 AGBG (no longer in force); § 307 para. 1 Building Code

"The BGH ruled that the frequently used standard contract clause 'Set-off ... is only permitted with an undisputed or legally established claim' in architect contracts, where a contract for work and services is assumed, violates § 9 para. 1 AGBG (today: § 307 para. 1 Building Code) and is therefore invalid. It is unclear whether this decision only concerns the law of contracts for work and services, for which it was made. ..."

I think that is essentially the same.
They probably simply did not change the contract for work and services back then or do not themselves know about the judgment.

Regards Yvonne