Lack of "Quality Control"...
That's a common problem with foreign ammo. Years ago, I decided to try Aguila .22LR, and bought a brand new 50 round box. One of the cartridges looked like it had been grabbed with Vise Grips and twisted! And my first (and only) box of Russian steel-case .223 or 5.56 contained a cartridge with the primer seated sideways & smashed flat in the primer pocket! As my good friend Captain Obvious always says, "Look 'em over BEFORE you load 'em in the mag!"
As far as Thunderbolt goes, it's been great in some of my guns; as @gunman42782 pointed out, .22s are finicky things! I keep as many different 'flavors' in stock as possible, because you never know if a .22 is going to prefer something expensive or something from the bargain basement.
As always IMHO, FWIW, YMMV, etc.