Corning PC-420D issue: Near-total loss of control

I've had my Corning hotplate stirrer for nearly three years now and have loved every second of using it. However, it has now developed an issue where the stirring and heating only initiate at full power. The stirring function completely ignores the adjustment dial, initiating as soon as the unit is plugged in. The heating element remains disengaged as long as its respective dial is in the OFF position. The equipment manual^[1] seems to imply that an error like this is known. Losing the use of the hotplate would be quite devastating and so I intend to fix the issue if at all possible. I figured that I might as well make a thread where I can document the project and ask for help.

First, some photos.

(Fig. 1) Stirring control dial with the knob removed. Prior to this I have never removed the knob (a no-brainer, now that I know I can simply pull it off) and have opted to use tweezers and a moist paper towel to wipe the surface underneath. The results are evidently poor and, while there is a rubber gasket underneath the 13 mm nut, I suspect that the inner shaft lacks such protection and can potentially wick moisture into the potentiometer.


(Fig. 2) Overall view of the unit with the bottom cover removed. This is the 230V model. To my untrained eye, nothing seems to be obviously fried, disconnected or otherwise out of order.


(Fig. 3) Top of the control PCB. This also passes my visual inspection.



I must emphasize that my knowledge and skills are quite lacking as they relate to working with electronics. However, I feel like I have arrived at a reasonable guess at where the issue might be. Apparently, inside a potentiometer there is a moving contact that turning the knob causes to move along a resistive track. The contact between these two parts is supposed to remain clean and lubricated. Otherwise, there can be disruptions which can cause the device to malfunction. There is an article which goes through the process of servicing two old potentiometers in detail^[2]. Upon reading it I suddenly recalled that indeed, the motion of the knobs on the brand new unit used to be incredibly smooth and realized that I must have gotten used to its gradual change into what I still consider decent but clearly a little bit frictional. As to if whether this actually is the culprit I seem to have no way of finding out other than to disassemble the potentiometers and clean and lubricate the contacts.
If you're reading this and have a different suggestion, I'd love to hear it.

Now, in the heat control potentiometer (fig. 4) there seems to be an abnormal (yet seemingly inconsequential) gap between the black plastic part and the metallic part of the assembly. This gives me some hope that the two portions are simply pressed against each other and that separating them might expose the contacts that I need to get to. (Optimistically) assuming this is the case, I would only need to detach the "top" metallic portion from the circuit board. For this, there are seemingly two different approaches:

1: De-solder and wick the three prongs from the board (fig. 5), or
2: Pry open the ends of the three prongs that are clamped onto the potentiometer. (fig. 6)

Either approach seems to have the potential for failure with disastrous consequences. I'm terribly inexperienced with the soldering iron (and circuit boards) so the second approach seems more attractive. However, I believe that the clamped connections are supposed to be permanent.

(Fig. 4)


(Fig. 5)


(Fig. 6)


I'd be grateful for any thoughts as well as advice for deciding on my strategy for tackling the issue!


References:
1: Equipment manual (Corning), section 7, page 9
2: Newgate Simms: Potentiometer Maintenance and Lubrication-Case Study