Error with Nucleo-H743ZI2, allocating memory

First tests with Nucleo-H743ZI2 fail. I want to do performance tests and do matrix-multiplications. I can do this up to 21x21 square matrices (float), the system crashes for larger matrices (22x22) (did that with other boards e.g. F446RE) up to 100x100 (floats), that worked perfectly)
Updated mbed-os to 6.3 (no difference).
Error links to:

but could not fix that

where did you define the array? If it is on the stack, it will be too large. It must be located global or on the heap with malloc or new.