This has already happened to your rig - that's why the other valve is white. I would replace the black valve with one just like the white one. That will be the easiest and is a good fix but you will have to surgically remove the two copper bands.
The bad and good; you have Qest tubing (NOT Pex) which has a sorted history. The tubing itself is great but the terminations are troublesome. However, you do have the better, copper crimps instead of the horrid aluminum parts.
The white valve uses internal compression to seal and will work better than what is there. Any RY parts store will have the white valve, just take a pic of it to show them. This white valve will be for Pex tubing but will work fine for your Qest lines
