Tamiya recently released a statement about static electricity building up in the TA05-R chassis, and potentially causing problems with your metal-geared servo – full statement here.
This is something I had never, ever heard of happening with another car, but I do think I have experienced the phenomenon myself. Mid-race the servo “lost” it’s neutral position and the car veered off the track, but switching off and on again caused it to go back to normal. It’s only happened once but obviously I’d rather not have it happen again.
Tamiya’s own suggestion is to fit the #53893 optional carbon moulded tub, which is conductive, but also quite expensive compared to the plastic tub, and stiffer which will affect the handling a little.
But now KO Propo have published their own solution to the problem.
First step is to take a 10cm length of fine gauge wire (approximately 1-2mm, KO recommend their own antenna wire), and strip the ends.
Second step is to attach the cable to the screws on the centre bulkhead and the front steering post. This should apparently give the static a route to discharge that avoids the servo.
KO appear to have simply screwed the wire in place. What I have also seen, and what may be neater in terms of assembly, is to solder the wire onto the screw heads.
Original instructions here.