Strange intermittant problem

aaron

Hi
I have Geeetech delta printer which I am slowly getting to know. However there is a strange problem that makes no sense to me at all. I usually have to set my print off 3 or 4 times before it will start to print. When it doesn't print it will do a G28 to home and the sit there for half a minute and then cut out just before it should go on and do an auto bed level. At the bottom of the screen it spits out '?Probe? Z Z?????????????????????????
If I start the print again and I am lucky it will do the G28, G29 and then start printing. As far as I know I haven't done anything that would change the configuration between times.
I would be grateful for any thoughts
Thanks
Aaron

Repetier

What firmware are you using?

IN any case returning so much ? seems not typical and repetier-firmware never would send that. If you can normally print without much errors I would assume the baud rate is correct, otherwise it might be a wrong baudrate.