Sigma flash erratic, only a year old

I have Sigma-530 DG ST EO-ETTLII flash which has been giving me excellent results in last one+ year I have owned. I bought it new but without warranty.

For last two days it has suddenly started behaving erratically. In TTL mode, it works fine for first five - six shots and there after it starts firing either with minimum energy or with maximum energy. After switching on & off couple of times, it does give one odd correct shot, otherwise continues with erratic behaviour.

Any one faced similar problems. Any suggestions on course of action are welcome.

The first thing that I would try is to change batteries. Make sure you have good batteries in the flash. I do not mean just freashly charged rechargables. They might be at the end of their useful life. Just for a test put some new alkalines in the flash and see if that helps. The other thing that will cause erratic operation in automatic mode is a bad hotshoe connection. Make sure that the contacts on both the flash and the camera are clean and tight.

Dedsen - Thanks. I will try both.