Don't worry at all, I will help in troubleshooting, all I needed to know if this is normal. I can tell you off the bat that there is no interference as it was far from those, but I did plug it into a laptop, both USB 2.0 and 3.0 (Win 7-64), and laptops do tend to have lower voltage. This is actually good that it happened as you are unable to replicate it - I have 6 computers with different configurations and will get to the bottom of this 
I have found the following so far:
- The test in windows (joy.cpl) works perfectly for both USB 2.0 and 3.0 for pulling, releasing is not so good - first 40% of the travel has no effect and it is "jumpy" after that.
- After testing it on several tables, it works, but again - the first 1/3 of the travel has barely any effect (but it does), and then the next 1/3 does most of the work, ending with no travel for the last 1/3. Release is really jumpy and inaccurate.
I will start experimenting later today and let you know.

UPDATE: three computers later... same identical thing (Acer laptop, Toshiba laptop, Gigabyte MB desktop). When releasing the plunger veeeeery slowly, the ball keeps getting kicked lightly several times during the release. The test table shows decrease in the decrements of 2-3, e.g. 24-21-18-15-13-11, etc. I emphasize "super slow" release. On the other hand, when I pull the tube off to the point where I have to hold it (at the very edge), the plunger pull gets distributed more evenly across the length.
I will post the video later today.
Here it is: http://www.youtube.c...h?v=ivbPVfZ5_UQ
Edited by dsasa008, 16 December 2013 - 07:43 PM.