The main thing that can go wrong is forex bots is that 95% of them use the same old classic indicators that fail when the market is moving fast or trending, another thing that happens is the market changes and the settings need to be reoptimize most fail on this requirement.
Its best to trade the pairs that best suit your trading strategy, also you must factor in money managment to make sure you have enough margin to cover trading alot of pairs....
Most brokers are just bucketshops that hedge against your position to profit when you lose.. So when you scalp there and make alot of cash they dont want to pay and just give you the boot...IF they are a legit broker they will always pay and help you scalp as you both will be making good money...