Massive VICOR module failure

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Dear all,

I have an old design, which use 4 VICOR modules (V24A48C400BL).
The schematic is an Serie/parallel operation. All modules are powered from single 24V battery pack.

2 modules are parallel wired configured at 45V output
2 others modules are also parallel wired configured at 25V output.

45V and 25V outputs are then wired in series to get +70V output.
The 70V ,output power a full bridge PWM amplifier.

The full schematic is attached to this post.

According to this VICOR NOTE  (page 9 figure 2.10): https://www.vicorpower.com/documents/applications_manual/fas_trak_apps_manual.pdf

Vicor module Sense must be connected after ORing Diode

According to this VICOR NOTE: https://www.vicorpower.com/documents/application_notes/an1_high-vout.pdf

Vicor module Sense are connected before "ORing Diode"
I put ORing between quotes because, as far as modules are not connected in parallel, thoses diodes are not oring diodes (to my understanding), but vicor said in it's note : Furthermore, D1 and D2 provide an additional voltage
drop to compensate for the forward voltage drop of D3 and D4 under this condition.

Additionnal protection diode are added (D3 and D4 on figure 1 of the note) => diodes D3 and D4 prevent the output from going
negative if only one converter is operational.

As you can see on the attached schematic, those protection diodes are not present in my old desing, furthermore, each pair of modules are switched on/off by an independant relay (short circuit PC and -VIN of the Vicor module)

This old design works like that for more than 10 years, and recently, i was troubleshooting something, and ALL the four VICOR modules burned !!

I feel like we have a design weakness. It is unbeleavable that the four modules failed at the same time. What do you think could be the cause of the breakdown?

One module did not start and the other had reverse voltage ? Vicor Said in another note than Sense pins shound be never driven negatively. In case of one voltage failure, the other module output in driven negatively isn't it ?
It can explain failure of two modules, but the others ?

Thanks in advance for your help...