Rebels are ridiculous

What the fuck is wrong with them? I created Polish-Lithuanian Commonwealth and every fucking 3 months i see 20k spawning in somewhere like these stupid volhynian separatists which keep spawning from 1444, can someone tell me how is it possible that WALLACHIA separatists are spawning in numbers like 17, 20 etc every fucking 5 years? And when i defeat them new separatists appear in fucking siberia, i have 0% overextension and -0,80 national unrest, it's impossible to play with army reinforcing whole time... PS: of course i don't have any disasters