HELP Plasma CNC has its own will

Hello,

We have a CNC plasma of Stako with a Burny 2.5 and a Hypertherm Powermax 1650.
This machine has some strange problems.

The problem become only when the NC files are large.
Like a 175 kb.

Then the plasma cutter starts allright but after cutting a few parts.
He stops halfway te part and goes to his starting point and will continue with existing part.
This is not intention because he cutting a part that already is cut.

Hes anyone a clue what may be the reason of this problem?

Thanks for the reply!