A tad different:
If there are two systems for the same strategy it increases the model risk, since the systems cannot reference each other. Thus the probability of an error rises.
The slippage potentially rises because opening a position with size “2” by two different systems with size “1” each, will lead to different prices.
The system risk doubles because maybe one system get’s shut down on the server side while the other system keeps running.
Using two systems in the case of partial entries and exits is a serious complication and should be avoided, in my opinion.