IMAT: rotation axis moves without being asked

At 2019-09-29T09:47:40 sample stack Y was asked to move, while it was moving the ROT block (Tom Phi Rot) also moved. This may be mechanical/electrical as i can;t see any request to move. Putlog gives:
```
2019-09-29T09:47:40 Changed PV: IN:IMAT:MOT:STACK:Y:SP new=150 old=-149.999
2019-09-29T09:49:27 Changed PV: IN:IMAT:ATTEN:OPEN:SP new=1 old=1
2019-09-29T09:50:14 Changed PV: IN:IMAT:ATTEN:CLOSED:SP new=1 old=1
2019-09-29T09:53:12 Changed PV: IN:IMAT:MOT:STACK:X:SP new=100 old=258.796
```
Looking at the galil motor log for galil 05, here axis B is ROT block (Tom Phi Rot), axis F is sample stack Y, axis C is ARC_LO block (Tom Chi L)
```
[2019-09-29 09:47:40] MOVE: axis F to 959997 (relative) current readback 1.29718e+006
[2019-09-29 09:47:54] Poll services: MOTOR OFF E
[2019-09-29 09:48:18] STALL: pestall_time=1.04916 (>sevr=major Encoder stall stop motor B
[2019-09-29 09:48:18] 1) encoderMove_=1 encDirOk_=0 _SCB=4 _BGB=0
[2019-09-29 09:48:18] Poll services: STOP B
[2019-09-29 09:48:18] STALL: pestall_time=1.08285 (>1sevr=major Encoder stall stop motor C
[2019-09-29 09:48:18] ) encoderMove_=1 encDirOk_=0 _SCC=1 _BGC=0
[2019-09-29 09:48:18] Poll services: STOP C
[2019-09-29 09:48:24] STALL: pestall_time=1.04918sevr=major Encoder stall stop motor B
[2019-09-29 09:48:24] (>1) encoderMove_=1 encDirOk_=0 _SCB=4 _BGB=0
[2019-09-29 09:48:24] Poll services: STOP B
[2019-09-29 09:48:24] STALL: pestall_time=1.07953 (>sevr=major Encoder stall stop motor C
[2019-09-29 09:48:24] 1) encoderMove_=1 encDirOk_=0 _SCC=4 _BGC=0
[2019-09-29 09:48:24] Poll services: STOP C
[2019-09-29 09:49:11] STALL: pestall_time=1.055sevr=major Encoder stall stop motor B
[2019-09-29 09:49:11] (>1) encoderMove_=1 encDirOk_=0 _SCB=4 _BGB=0
[2019-09-29 09:49:11] Poll services: STOP B
[2019-09-29 09:49:16] Poll services: MOTOR OFF C
[2019-09-29 09:49:20] STALL: pestall_time=1.05108 (>sevr=major Encoder stall stop motor B
[2019-09-29 09:49:20] 1) encoderMove_=1 encDirOk_=0 _SCB=4 _BGB=0
[2019-09-29 09:49:20] Poll services: STOP B
[2019-09-29 09:49:22] Motor and Encoder are in sync by 0.0429 < 1 egu
[2019-09-29 09:49:22] MOVE: axis F to 119.84 (relative) current readback 2.25718e+006
```
So no apparent request to axis B (ROT) however the axis is reported as having stalled, this may becasue encoderDirOK is false as it is moving opposite to last move. Axis C is also in motion at some point. See attached graph.