Hi Louis,
thank you for your attention 
At first, as LED drivers or “shift registers” on my modules are used: FM TC5020A, according to its datasheet, supply voltage area, 4,5V to 5,5V, so I set to 4,5V, why?
Input high threshold voltage is 0,7 * VCC, at 4,5V it is 3,15V…very close to 3,3V, but in specification!
My new test program is a simple pixel hopper, shift a blue pixel with ‘w’, ‘a’, ‘s’ and ‘d’ in the matrix area.
Result is very interesting!
Every second step everything is off and in between two pixels are switched on.
So the more interesting thing: It fits to the data output of I2S interface.
I my case it is not a HW issue, it seems more related to software.
I tried to half the I2C clock speed via:
#define ESP32_I2S_CLOCK_SPEED (20000000UL)
to
#define ESP32_I2S_CLOCK_SPEED (10000000UL)
but this dopples everything on my led matrix (64x32)
But pictures are somtimes more…
Pixel 0,0 should switched on:
Pixel 1,0 should switched on:
Pixel 1,1 should switched on:
Waiting excited for next ideas