Went out last night to shoot fireworks. Set the camera to bulb, manual focus etc and it took the first shot perfectly, ie clicked remote to start, and clicked a few seconds later to . The next time I clicked, despite still being in bulb mode, it did a really quick . Tried again same result. The only way I could get it to wait for me to click to the was to turn off the camera, turn it on again and it would perform perfectly - once. If I tried for a second shot a quick would be the result. So, being in the dark with other photographers around me I just kept turning it off and on again. Very frustrating.
Can't work out why it is doing this - have done this before and never had this problem. The camera is a D7100. Hopefully someone can point me in the right direction. I assume I've changed something accidentally but I have no idea what.