If they are too tight, it may be that the contact part of the connector was somehow bent, and may not be putting even pressure on both sides of the connector. be sure to always take a quick look into the connector housing to insure that both tips sit in the housing the same, and that there is no cracking or flexing of the flat piece of plastic (down inside the housing) that puts the pressure on the spring. be sure to check all 3 halves (truck, charger and battery) and be sure to make sure that the charger half does not lay on the floor where it can get run over, running over the charger half is what sometimes puts a bend in the metal parts that creates a bad connection, which in turn creates heat while charging that can eventually cause a failure of the matching connectors (battery then truck), although the battery connection is not supposed to be something a child could disconnect, (and so a small women may have difficulty. also).
The type of connectors you have now, (that we are talking about so far) we call "SB" style connectors. as work arounds, there are other types of connectors available that may work better for you, but may be more expensive per connector. but may also last much longer. You may want to consider the EC style connector, as it has a cam lock type lever to insure connection, that takes less effort to disconnect. there is also a YC type of connector, where the grab handle is part of the housing.