Student pilot reported dual ECU failure in their DA40 and a safe return to departure airport.

Narrative

During this flight; me and an instructor were taking off XXL; and experienced a brief ECU B failure; which lasted about 3 seconds before clearing. We took note of this; and continued to ZZZ; our first airport on our route. We landed without incident.After our first takeoff at ZZZ; we noticed that we had a dual ECU (Engine Control Unit) Failure. I immediately pulled out the QRH and followed said checklist to the line; where after introducing 50% power; the ECU A failure cleared; while ECU B remained latched. I intended to land; and run the checklist on the ground; to see if it would clear. The instructor pilot said we should continue with a few touch and go's before making our final decision. After our final approach to landing with the ECU B failure annunciation still latched; I advised we should land and take said checklist action. The instructor pilot said that is not be necessary and we should just take it back to ZZZ1; with ECU B fail annunciation still latched. We flew back to ZZZ1 after a touch and go at ZZZ2 without incident.