Stuck COM ports on various instruments

MOXA com ports appear to get "stuck" on various beamlines, in various situations. The symptom is that "access is denied" to the port even though no process is using the com port. This means that the COM port is effectively useless after this issue occurs. You cannot even connect to the port in this state, windows commands like `MODE COM5` will just return `access denied`.

This has (recently) happened on:
- RIKENFE Danfysiks, https://github.com/ISISComputingGroup/IBEX/issues/4376
- ZOOM a labview Mercury ITC driver was the last to use the port, https://github.com/ISISComputingGroup/IBEX/issues/4421
- MERLIN TPG x2, https://github.com/ISISComputingGroup/IBEX/issues/3527
- Others

In this situation, rebooting the MOXA has no effect. The only ways we have found to solve the problem are:
- Reboot the NDX control PC
- Move the affected device to a different physical port

This ticket is to investigate the problem further to see if we can reproduce it in various conditions. If we can, then either fix our drivers or escalate the problem to MOXA support as appropriate.