Let's assume I clone one of my wallets and place it in two servers totally unconnected with each other. Let's call it "left network" and "right network". I use same inputs and send a transaction of 10 BTC and from the other wallet I send the same transaction, but with a value of 5 BTC (same inputs, though). Note that I am sending both the transactions at the same time.
Now, the left side will believe that I sent 10 BTC and the right side will believe that I sent 5 BTC. How will this dispute be handled? Please take a look at the image for some understanding:
https://ibb.co/cVBEAG