Its the dropouts, and because the right one is short, there's issues with the tensioner.

The bike shop said to bring her back when I have the money and they'll order in a better one which will help with the dropouts, but for now I'll ride her.

 Thanks brother. She rides smooth, just the odd disconnection on the gearing every so often. I'll take her for the odd rides now and again, then get the tensioner issue sorted.

 Thanks mate . There's a problem with the tensioner, but I'll get that sorted next month when I take her back to the shop.

 Thanks buddy. And yup, I'm already on it. I'll adjust the seat ASAP.