Reflectometry: Invalid position stops move all working

Reproduction steps:

1. Set Theta to 45
1. Click move all
1. sp rbv is no updated (although doing a caget reveals it should have)
1. change Theta to 4.5
1. Move All
1. Still error move does not complete

This is an outside case so can be done after mvp.

### Acceptance Criteria

1. Theta is moved to at last step
1. sp rbv should be reverted [this makes this a big ticket]