Some shutter open/close values do not work with subframe sampling

**Describe the bug**
There is no motion blur with shutter open/close values like -0.1, 0.1 and subframe samples.

**To Reproduce**
Steps to reproduce the behavior:
1. Extract [subframe_mb.zip](https://github.com/user-attachments/files/21475919/subframe_mb.zip)
2. **kick arnold_repro.broken.usda** does not have motion blur. **arnold_repro.working.usda** does. The only difference between the two is the shutter open/close values.

**Used Software Versions**
- Arnold: 7.4.3

Extract subframe_mb.zip and run `kick arnold_repro.broken.usda`, then compare it with `arnold_repro.working.usda`; the shutter open/close values are the stated difference. Reproduce the missing motion blur with Arnold 7.4.3 and trace the subframe sampling path to determine why values such as -0.1 and 0.1 fail; done means both files produce the expected motion blur.

Written by the indexing model from the issue text.