pressure switch chattering

We replaced our jet pump and pressure tank about a month ago (3/4 hp 1&1/4" intake). We live rurally and I was working out of town when the pump caved. Since the wholesalers in town were closed (it being Sat.) I sent the wife to town to purchase a new pump from a big box store. The pump's fine but came w/ a 20/40 pressure switch. Re & re'd pumps only to find that the old pressure tank's bladder got compromised. Off to town myself for new tank. New tank installed but couldn't get the p.s. on the new pump to adjust to 30/50 setting. Installed p.s. from old pump and it's sort of worked but time to time started cavving (contacts chattering) badly. I don't know how many times we've drained the system checking tank pressure, making sure the inlet tube to the p.s. was clear, and bleeding air out of the domestic water lines. Enough was enough, and today went and got a new switch preset to 30/50. While bleeding out all the lines it dawned on me that previously we never bled the hot water line to the washing machine (we only do cold water washes), though the hose was hooked up to the washer the shutoff valve was always closed. Everything's working like a charm today so my question is was that enough air in the system to create the chattering? And are chattering contacts always related to air in the system? I can totally relate to the unhappy wife and daughter fella.