Be aware of a small but effective button AEL button - Auto Exposure Lock button. Some user's have experienced that when lifting the camera from a table or tripod the small button can easily be touched and AE mode enabled for the next shot. We have from support seen this which causes frustration but also relief when the cause is founded - the button for Auto Exposure lock - AEL button is activated although this was not the intention.
When shooting in the different modes the exposuretime or aperture will be set to another parameter than selected when the AEL button is activated due to the function of AEL. Be aware of not touching the button when shooting as settings may change from what was selected.