I had a similar problem with my Walther Nighthawk. Even trying different brands of caplets including the lubed Walther ones didn't help - I thought the seal had gone.
A Very Nice Chap at Bury Gun Room told me that the brass screw seal on the drop-out CO2 mags have a tendency to work loose, and to try tightening the screw before fitting new seals, and it worked a treat!
If you can get to it on the PPK, give it a go first.
And buy lots of pellguin oil. A very nice chap on here sells it.
Have to agree...do not own a Co2 weapon without owning Pellgun oil...
Eric.
Oh yes, I regularly oil my weapon with Pellgun
Russ
Air Arms S400 Classic - Hawke Airmax 3-9x40 AO MAP6, SMK QB78 DL - JSR 4x40 Mildot ill.El Gamo ASI sniper, BSA Airsporter MkVI. UBC#22 - Sheridan EB22, Gamo Compact:R77-4:Falcon, Walther PPK, CP88 shiney, SMK G10, Baikal 53M:MAK, Crosman 357
My wife ought me a Walther PPK last Christmas... (with the laser sight) to replace my 25 year old Crosman 1200. 'Not happy with the PPK at all. 'Doesn't seem to have the range nor the velocity of the Crosman. The laser is worthless. I've tried that from a gun rest, but usually anything past 20' is anywhere but where I point it. The C02 ctg is difficult to seat... 'foolin' around with that internal length thing, then twistin' that infernal butt plate doo-dad. I use Daisey C02 ctgs... 'no ruff edges but gettin' a decent cartridge puncture is a trick. I'm gonna be buyin' another Crosman. The Walther is OK for point-defense practice at close range... no aim, just pull, point 'n shoot. (Open carry is in the Arizona Constitution... Article 26. I have an AZ CCW permit also...)
My 'normal' carry gun is a Springfield Armory 1911-A1 in .45 acp, which is a tad largish to conceal anywhere.