I have several crown SP320 trucks and i seem to notice a trend of plugging issues with these trucks. Ill get a truck in my shop and the operator states that the truck will not plug usually only from reverse to forward. so the first few times i would just replace the contactors and away they went no further problems. then i started to notice that the same truck would be back 2 months later same problem and i know that there is no issue with the contactors (brand new). so i guess i am looking for any other suggestions on where to look what to check and so on and so forth any help would be great.