FX Getting Set for Warmer Weather

I finally got the Maverick out of storage (spent the winter focused on my powder burners). Once I wrapped up the quick tune-up (inspected and lubed all o-rings, replacing a few), I got right back to shooting some stellar groups from my typical 75 yards. After polishing off 2 tins of JSB 34gr pellets and a few refills, I started to notice a small leak. I didn’t think anything of it at first, I typically lose 10-20 bar after a fill. But it’s been about 4 days since I last topped off the tank and haven’t had a chance to shoot since then and I noticed I’m almost down to 100 BAR (filled the tank to just under 300).

Considering the amount of pressure lost, I’m assuming I have a leak somewhere. I know it’s not a matter of storage location - considering it stayed the same pressure throughout the entire winter while sitting in the basement (no moisture / humidity and temperature controlled). I can’t seem to find the source of the leak, even after checking inside the block.

I’m looking for any suggestions on where I can look to find / fix this leak.