Try printing on one unit at a time and see if it keeps running. It is possible you have an air leak in one of the short stroke pistons which put each unit on impression. If one of these are leaking (There are 2 per unit.) the air compressor will drop below 6 bars and shut off the press. The only way the press will start running again is when the air presure gets back up above 6.5 bars.
If by chance you find it is one of the short stroke pistons, I recommend you have it put on by a qualified technician. The air ram has to be measured exactly as the one that was in the press when replacing. If not you can actually cause the bearer pressure to change and cause the back lash in the helical cut drive gears to change as these are paralled at the factory. You won't notice it right away but a 1 year or so down the line you will have caused serious irrepearable issues with the print quality.
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