300+ pro ESC is going OFF please help

[serc]

Hi people,

To run an old surfboard I have 14s lipo 51,8v 20ah with a lehner torqstar 7040 motor winding 6 = 288 rpm under load, with a MHZ jet drive 64mm and a Swordfish 300+ ESC.

The problem is, that the ESC is going off at more than 50% throttle.

It just goes off and restarts again with the beep beep sounds, then it will work again.

It is taking about 75A and 55v.

I tried LVC different settings, and also 7.2v LVC and 2.5v per cell
I also replaced my UBEB for an old fashion 4x AA battery 6v to be sure the receiver gets enough power.
I also tried to go from 14s to 12s
I also tried to increase throttle really slow.
Temp of ESC is only 45 and a peak of 58 degrees celcius.
Voltage drop is also very little
Motor and ESC have good water cooling.

What I did not do yet, is adding a capacitor bank, I know it is suggested, but since I have such a big battery with 20AH and 25C-35C batteries I did not install this yet.
Is it possible that it has something in common with my problem?

What else can I do ?

See attachments for data.

[serc]

Here is a .jpg from my log file. It does not show all data in the curve.

I also can not make a log from the esc going off because if the esc will go off than the log file is also not saved into the ESC