Check if your power plug is the correct size and specification.
Very often this can a bad connection, the board receive current at plugin and then the “loose” plug sporadically does not make a good contact and loose the power.
The power supply circular plug MUST be 4.75 x 1.75mm and nothing else. If this one is not exactly the size you might have a bad connection.
Other be sure you are using correct power supply specs.