Quoted from OLDPINGUY:

TSPP, in general feedback, can have 3-5 inserts that ghost. (The last one I did had the left in lane ghost too)
A few NG bulbs should solve your needs, an OCD board is a good option too.
Whats also fair to share is to be sure if you have any additional LED Mods, that they may have their wires reversed.
The last 3 weeks alone was about 6 pinsiders, with dozens of emails, over ghosting, which was solved with the reversing polarity of Mods they had installed with alligator clips.
Equally, I often hear of "ghosting" that turns out to be a resistor or diode.
Start with the simple answer first and work from from there.

Quoted from OLDPINGUY:

The cooling towers are 6.3V, so I would not expect any issues if you put 12V...but why not use 6.3V? or take out and test.
If the issue is, as you describe, a couple of inserts lighting faintly, when they should be off, it does sound like ghosting.
Some of the other replies are describing how LEDs behave in attract mode.....they cant fade, so they flicker...this is solved with OCD. If it, during game play, and its a faint lighting, it can flicker too, this sounds more like ghosting.
If they were flickering at fully lit, its a different issue.
Sometimes ghosting shows up later, ie, Jackpot lit, 2nd itchy and scratchy, and then extra ball lane.
Play the game a while, and see which ones bother you, or show up to take the first step, NG bulbs to solve.
Maybe a friend, fellow pinhead nearby has some NG bulbs, to try first.
Its not uncommon, and one either has the choice of fixing a couple afterward, like you, or spending, as kits or even self done, all inserts NG, which is $20 or more more. Hopefully, youll find your need to be just a few bulbs and done.
If you wish the full affects that incandescent has...fades and swipes, an OCD board is the best way to restore those effects,