Zen-Fire

Zen-Fire doesn't supports OCO order submitted from Multicharts and thats's fine. Can someone explain me, why every time I modify an order from 2 orders pair, another order is cancelled? (I'm submitting Buy @1100 limit and SellShort @1110 limit and modifying Buy @1101 limit).

Please make order submission engine work correctly. Multicharts are not in hobby business, it is serious money business and this kind of errors are not acceptable.

I am not sure if I understand you fully.
I would be very worry too if there is problem.
Can you post the log, with notes pointing to the sequence of errors?

1) Submit 2 orders
Buy next bar at 1100 limit
SellShort next bar @1110 limit

2) Event in market prompts you to modify one order and submit
Buy next bar at 1100 limit
SellShort next bar @1109 limit

3) look in NT Orders tab:
The Buy order was cancel and submitted again additional to Short oder.

Only Short order should be canceled. Zen-Fire doesn't support OCO and those 2 orders are independent. Worst, same happens in the pair if one order i target and one is stop. When you modify your target (you are long, lower target because market is going against you), the stop order will be canceled and by moment your position is unguarded.

I own Multicharts. I did not use them last year. Latest improvements to supported brokers make me look again. I'm really surprised, how basic things are not working in advanced product (release 5.5, so I'm expecting that is advanced and tested). Multicharts, time to get serious because it is starting to be a shame.