Help Printing 'One at Time' - can't get it to slice.

[curaMatt 1]

I'm using a Creality Ender 3 V2 trying to print two small objects using the 'One at a Time' option, and no matter how I arrange them I cannot get them to print:

 

 

As soon I pressed 'Slice' it reduced the build volume to avoid the gantry clashing with the prints, but now it wont slice. I can't see how the gantry (25 mm height) could collide with the first print in this case regardless of how low the gantry was since the models are spaced very far apart.

 

Any way to fix this?