My Tektro R539 brakes do work on the road: they obey to the brake levers at squeezing and releasing times. They do not behave to the mechanism to open them (for wheel removal for instance), they do not spring back (= open wide) when I open them. As if the spring is unable to open.
Outside of minor maintenance (centering and aligning the pads) I have not touched them, except for scrubbing the dirt from the spring with a metal sponge (I was using it softly). I also may have touched the lock plastic thingy (see https://www.tektro.com/products.php?p=44) without intent. I have tried putting some WD40 on the cables, to no help. It's odd that until very recently the brakes had no problem opening.
Should I refrain from cycling until I fix this?
Edit, here are pictures of the brakes and cables:
Edit 2: I have replaced the cables with new ones. The brakes are now opening when using their QR, not fully springing open as I have had it in the past. Enough to brake on the road, plus remove the wheels when needed. Home repairs by Mister Good Enough™. Thanks for the help all!