Usual problems caused by the AdBlue system are tank issues, heater, nozzle NOx sensors error codes, NON-START problems. Repairing these issues can be really expensive and painful as many manufacturers struggles to provide replacement parts in time or within a decent price range. 
Its purpose is to reduce NOx emissions. AdBlue is a mixture of urea and water injected into the exhaust system, converting NOx into nitrogen and water vapor. AdBlue Removal reduces running costs, improves fuel consumption, and vehicle performance. It also eliminates the need for AdBlue fluid, increases power with remapping, and reduces emissions. Different options include AdBlue emulators or modifying the ECU file without mechanical changes.