Stinky soft onions

I had a really good crop of onions this year but they haven't kept very well, I have just sorted throw about 100 onions and had to bin about 30 and at least another 50 are starting to grow again
Is this because of the poor weather we had this summer or am I doing something wrong?
Last year I had a dozen or so that started to regrow but this was late in the winter as the spring started so half expected this. They are stored in onion bags hung up in an unheated conservatory same as last year.
Looks like an onion soup making afternoon is on the cards 

They didn't bolt but a few always have thick necks so these get used up first, I only kept the good ones for storage 

I stored some onions in my poly tunnel and they went the same as your onions, I think it may have been condensation. The ones that I stored in the shed are fine and are from the same crop. CC