Hi,
. I will start with checking the faults in ABS system when the broblem is happen - if you can not talk to the module ( I have seen this many times) ABS module is bad. Then module goes bad , ABS light comes ON and brake light flashes.
There also may be a problem with connection somewhere in the harness. maybe one ground or power splits into systems which do not work , ( need wire diag. by VIN).
this is where I will start.
good luck