24V to 12V converters getting burned/ruined

I have 3 x 400W panels in series and connected to MPPT charge controller. The panels put out 45V and 9A each. So 3 in series gives 135V and 9A. The MPPT will accept 160V. Have a battery 8 x 314Ah LiFePO4 cells in series to make a 24V system. Connected on the final negative of the battery is a JKBMS. The P- of JKBMS is connected to 24V to 12V converter. The P+ terminal of battery is connected to 24V to 12V converter. A 12V to 120V inverter is connected to the 12V side of the 24V to 12V unit.

The system seems to work fine until the battery gets to low state of charge. Something is happening when the BMS turns the discharge circuit off to protect the battery cells. The symptom is that two different types of 24V to 12V converters get ruined such that they stop functioning. Both brands of 24V to 12V converters stop converting. I have tried the el-cheapo silver boxes with 3 connections that are readily found on eBay at around $45. The silver one I tried was rated at 60A, 720W. I also tried a Victron 24 to 12 rated at 70A, 840W. Both of these units now fail to convert 24 to 12 and both stopped working permanently when the battery was shutdown by the BMS—even after the battery was charged. Both 24 to 12 were removed from system and a 24V source was connect to the input and common and there was no voltage on the output and common ground. Both types are non-isolated type 24 to 12 converters.

The system worked well for about a week with the silver no-name 24 to 12. It stopped when there were 2-3 cloudy days and the BMS turned the battery off. Then after charging the batteries, the 24 to 12 did not produce 12V on the output terminal.

Does anyone have any idea what I have done wrong? I am tired of burning up 24 to 12 converters. At $50 a piece and more for the Victron unit, I need some help. It is getting expensive.