MatterControl leaves tasks running if slicing is cancelled

[Tim5151]

Bug Report

I have 2 Voxelab Aquilas named in MC as Aquila #1 and Aquila #2.
Number 1 connects through Com 6, #2 through Com 9 (if that matters).
I wanted to print 2 copies of a model, one on each machine.
Opened #2, loaded the model and sliced it no problem.
Opened #1, loaded the same file and started the slice.
Writing the layers stopped about 9 layers from the top.
Waited 10 minutes with no change.
Clicked on the square "stop" button to cancel the slice.
Nothing happened. I could not get control back from the slicing process.

Eventually, in frustration, I closed MC and restarted it.
I repeated the above procedure 2 more times.
Each time, the model for Aquila #2 sliced fine.
And each time, writing the layers for Aquila #1 stopped at the same layer, just short of the top layer.

So I switched to Cura and made my prints from there.
I had to so so with only one printer, as Cura is unable to talk to more than one printer at a time.

But.... I noticed that slicing in Cura was dead slow compared to normal.
I gave up and went to bed, leaving Cura printing the 1st copy of the .stl file.

Today, I brought up Task Manager to see why EVERYTHING was running slow.
I found that three instances of Matterslicer were running and keeping my computer at 100% load!
MatterControl was NOT running.
At that moment only Chrome, one instance of File Manager and Cura were running (though not printing).

I did a warm reboot, started MC, and tried to slice that same file again on the Aquila #1 tab.
Tabs for both printers come up at startup.
I changed layer height from .2mm to .3mm.
Same issue as yesterday.
Writing the layers stopped just short of the top layer.

I've attached the .stl file, if that will help, but it slices and prints fine in Cura.
Also prints OK on the Aquila #2 tab where it again sliced fine.
I've also deliberately created the same issue today and made a couple of screen shots to illustrate.

Any more info needed, let me know.

MatterControl Build Number
2.22.04.11498

Operating System Version
Windows 10

Printer Make/Model
Voxelab Aquila running Alex's firmware: (Marlin-JyersUI Build Number v1.3.5)

Here's a ZIP file with the .stl and several screenshots. HTH
Bottle Holder.zip