it is possible that a screw that locks the linkage parts in place has slipped, causing it to pull the throttle slid open slightly when the throttle servo is at neutral.

its also possible that you could adjust the throttle servo trim to correct the issue.

but it may not be a linkage issue at all(tho check it fully 1st) it could be that a temp change is allowing the engine to idle higher at the current idle setting. a 15 degree temp change in the weather will change the proper idle screw setting needed to keep the wheels from truning when the throttle is at neutral.
if you make an adjustment, make a VERY small one! all needle adjustments should be made in very small amounts. getting crazy with the needle settings whenever a problem arises is a mistake many (including myself) tend to make.