In Texas, how do you challenge the validity of a mechanics lien filed by lower-tiered subs and suppliers when they haven't properly sent monthly preliminary notices? The project is non-residential.
You should consider preparing a letter to mail by certified mail, return receipt requested, to the invalid lien filer to set out the facts and to demand the relief that you want. Point out why the lien is invalid. Make sure that your letter is professional and business like as it may be evidence later.
You really should retain a construction attorney to review and evaluate your legal position based on the contract and pertinent documents. The right to be entitled to file a mechanic's lien is set out in Texas Property Code Chapter 53, and you really need to make sure that the lien at issue was filed improperly or inappropriately.
In your letter, you may point out that the filing of an invalid lien could subject the filer to liability under the Texas Fraudulent Lien Act, and the filer could be liable for statutory damages of $10,000, or actual damages, whichever is greater, plus attorney's fees.
If the lien filer persists, you may consider filing suit in district court to have the court declare that the lien is invalid.
Good luck.