I had key trouble like you experienced early on – an inability to easily get it in the slot – and at one point very great difficulty getting it out again!
I detected that the plastic had split and the RF chip had shifted a bit inside making the key very slightly thicker.
Back home I cracked it open. The chip should sit in a slight indentation on one side and has a litle dimple to hold it in place. I superglued it and clamped it tight and it has been fine ever since.