Apeks cylinder valves have always been shite as long as I can remember. Most of what they sell is shite and has been for a very long time (I don't know how much they actually make, most of their stuff looks cheap rebadged crap). As Iain HSM liked to say a bit more graphically, they've been trading off the back of a single product with no real product development for decades. It's exactly what happened to Poseidon in the late 90's. I suspect they will disappear entirely within the Aqualung brand fairly soon.
I quite like my Apeks regs. I've probably got about 10 of them. But they are all T and TX series, it does seem quality control went down the bog after they were bought by AL. I've never had any real issue with mine despite not being particularly careful with them. They used to be a commodity regulator, if you needed a load for a project then they were cheap and reliable. Now they are neither cheap nor reliable. I'd probably buy Scubapro if I was buying regs now, the only thing that puts me off is I know how to pull apart and rebuild my Apeks and no idea where to start with SP.