"attempting repairs yourself may void whatever warranty you have."
This is incorrect, at least in the U.S.
The " Magnuson–Moss Warranty Act" - a U.S. Federal law, "... ensures that consumers retain the right to repair these devices independently or through third-party repair services without voiding their warranties."
https://en.wikipedia.org/wiki/Magnuson%E...

It's not clear to me what part(s) is failing on the control board. The common problem is that the touch sensitivity decreases so one fix is to
decrease the resistance by adding the bolt/washer.
Your light seems to be more extreme that what I observed when helping my friend repair his Ottlite.

If shoring the wires is working for you, you can consider installing a pushbutton switch in the panel somewhere and connecting the wires to board, as you tested. You'll need a "NO" SPDT pushbutton (NO = Normally Open, SPDT = Single Pole Single Throw.)

Something like:
https://www.amazon.com/Waterproof-Moment...

Or, maybe someone will figure out which part is failing on these board and describe how to obtain and replace the part.

Two types of batteries for the Q325U with different power connectors:
C21N1624
C21N1706 (shown in this guide)

Uh oh! That's a serious safety hazard.
Have you contacted Ego support? I'm sure that would want to know about this!
And, I'm sure we're all interested in hearing their response.
- Wayne

It could be. The safety switch connector is a poor design and the mower vibration causes the connection to intermittently fail.

Oh, right, it's an LED!
The proprietary Ottlite control board probably uses PWM (Pulse Width Modulation) to control the brightness -- this is very common with LED lighting.
So, the question is, does the circuit provide current-limiting? An LED directly connected to a DC source will draw as much current as the power supply can provide, which could result in blowing up the LED(s.) Maybe there's a current-limiting resistor on the LEDs board? Or not?

One approach would be to use a 1K resistor in series with the DC power supply and the LEDs. That will probably be too dim.
Decrease the resistor value lower until the brightness seems right.

I can't find a schematic diagram for the Ott light, so I don't know if there is a workaround to the problem you are experiencing.
Since this is a fluorescent light, it needs high voltage, which is generated by the control board.
If you have a multimeter, you might want to test some obvious things:
- Measure the output of the AC adapter at the barrel connector. Is it 18VDC or so?
- Plug the AC adapter into the Ottlite control board. Is there the same DC voltage on the jack on the control board?

- Any components obviously bad? Burn mark? Swollen capacitors?

Good luck!
- Wayne

That would be an interesting reverse engineering project.
The guts of the Ottlite electronics is a dimmable fluorescent lamp driver, which is pretty easy to understand.
Maybe some other touch switch circuit could wired into the Ottlite board? Or, even just a simple pushbutton to avoid the whole capacitive touch circuitry, which, apparently, the Ottlite engineers didn't get quite right.
I did this repair for a friend, so I don't have the board to look at. But, if you learn something about this, be sure to let the ifixit community know.

The user manual suggests that the dimming levels are fixed and cannot be changed:
https://products.ottlite.com/p-463-dual-...
...
3. To power LED settings, slightly touch the switch (E) to achieve the following:
•turn lamp “ON” to 1st brightness setting; touch the switch “once”
•for 2nd brightness setting; touch the switch “two-times”
•for 3rd brightness setting; touch the switch “three-times”
•for 4th brightness setting; touch the switch “four-times”
•to turn lamp “OFF”; touch the switch “five-times”.

...

Sounds like your lamp has a different design.

A photo would be helpful. If you can take a picture and store it on a web site (http://photos.google.com, http://icloud.com, ...), you can reply with a link to your photo(s).