Everyone hates punctures, right? However, puncture is easy to fix while on the road.

Presta valves on three different inner tubes failed three times in a row. Where to spot the problem? I inflate tubes to recommended pressure. Tubes were: 2x Maxxis Welter Weight 700c, 1x Panaracer Greenlite. The pump is BBB "no model name" compact cheap pump with lever. After inflation the axis of the valve seems like curved slightly, so I guess, the pump somehow damages the core of the valve. Where to look at?