shower screwdriver stop assembly leak

I had a drip in my Delta Monitor 1400 shower which I think I've fixed by replacing the RP19804 cartridge (info found in this forum which I appreciated). In putting it all back together I notice that there is a very slight leak in the cold water side screwdriver stop assembly valve. A tiny drop will appear there every now and then. I was wondering if anyone had any suggestions on how to stop that? I'm not sure if there is something like Loctite that is appropriate for this or not.
tks for any info

Stop Valve

Do you have it completely open? A lot of stop valves tend to leak when not fully open or closed.