I think i know what you mean and i have a similar floor pump for my bikes. Always make sure that you undo the valve first which i assume you have done as you have lost more air. It is a knack to getting the pump to lock to the valve and my lever can turn either left or right and i can never remember which way to turn it so i too always lose a little air before getting it right. I think you just need to try a bit more but i know what you mean about it not locking onto the valve, it feels like it is fighting you to do this. I just wiggle it about until it allows me to lock the pump with ease. Sorry i cant be more technical but i hope you manage to pump up your tyres soon!