POLARIS: Investigate a potential ignoring of an error by IBEX from the Rotating Sample Changer

[KathrynBaker]

As an instrument scientist on POLARIS, I want to know why IBEX thought a sample was in the beam when the Maclennan crate was displaying an error.

Acceptance Criteria

1. There is an explanation as to what happened in the comments of this ticket
2. Any tickets needed to avoid this situation occurring again in the future are created

Notes

1. The first comment contains the content of a Footprints that was submitted to motion control
2. This may be related to Rotating sample changer: changes from tests of 4028 #4287, at least as far as methods of resolving it go
3. POLARIS/HRPD/GEM Sample Changer #2173 was the ticket that created this code and has some potentially useful information

[KathrynBaker]

The Polaris sample changer Maclennan control crate indicated an error -
position 3 requested, but the sample had failed to lower. However, the
Move_Finished block indicated "1" (i.e. it though the move has been successful)
and started the next run with no sample in the beam.

[Tom-Willemsen]

As discussed in planning meeting: I have merged the relevant information from this ticket into #4287 as we feel they are probably the same issue.