Firstly, I'm using a Nikon D7100. I went out to shoot some local fireworks last night and for some reason the bulb mode was playing up. Previously I've set it on bulb mode, clicked the remote when I hear the woosh of the firework then click the remote after the burst of colour to stop the exposure and repeat that process during the display. Last night it would take the first shot but when I clicked the second time it would just take a fast shot without my clicking the shutter closed. I switched to time mode and similar happened although on a couple of occasions it allowed me to do two or three longer exposures before just taking a really quick exposure. Switching the camera off then on again allowed the one or two longer exposures then back to ignoring the remote with a really quick exposure. Very frustrating. Any ideas as to why? I probably haven't used bulb mode since the last time I shot fireworks 12-18 months ago and don't think I've changed any settings on the camera in the interim.