All two bladed, teetering designs are susceptible to mast bumping. UH-1, 206, R44, R22, makes no difference. Get into low or negative G's with these machines and those like them at your peril.
People like such machines because they are economical to build and operate, and require less storage space.
Clearly, being the smallest and lightest helicopters of this type, the R22 and R44 are going to be more susceptible to external conditions that could cause unwanted low-G conditions, i.e. it takes less turbulence to cause a problem in an R22 than in a 206 or UH-1. Similarly, the R22 and R44 will be more susceptible to ham handed pilots.