ASUS XONAR ESSENCE STX II Burson V6 Vivid Opamp

Unfortunately, one of the op amps from the Supreme Sound Opamp V6 kit - V6 Classic, Dual x 2 ordered on 01/27/2020 and received on 02/18/2020 turned out to be defective. Unfortunately, I can to check it only today (03/13/2020) and what was my frustration and disappointment. The fact is that after 5 seconds - up to 5 minutes after switching on normal operation, the signal level drops by half and when the player stops, stray noise similar to an AC is heard. The previously purchased Supreme Sound Opamp V6 - V6 Vivid, Dual x 2 kit (shipped by your organization from China) works great, but the Singapore speaker proved to be defective. How many of your hourly tests? and what is the way out of this situation?