Will a third-party repair void our curtain wall warranty?
It can. Many façade and sealant warranties are conditional on approved materials, compatible products and authorised applicators. Before repairing during a warranty or defects liability period, read the warranty, notify the original contractor or supplier in writing, and invite them to attend testing. Keeping test records protects both the claim and the repair.
From the RRD Field Guide, checked against the sources cited in Façade and Curtain Wall Water Leakage: How to Diagnose and Fix the Root Cause. General information, not advice for your project.
The fuller picture
Façade leaks are diagnosed by mapping when and where water appears, ruling out non-façade sources, then reproducing the leak with controlled water tests: AAMA 501.2 nozzle testing for curtain walls and ASTM E1105 pressure-chamber testing for windows and walls. Test from the bottom up, isolate one joint at a time, and repair the proven path rather than re-sealing everything.