Mine does that about as often but it will usually only do it a couple of times. The first time it happens, I start off slower and most of the time I will feel it engage then it's good to go. After a couple of those it seems to be fine. I noticed it happen last summer so I don't know how long it will last, I figure if I am easy on it when I initially take off then it won't really get worse but I would like to hear from others. I plan on getting a new transmission soon just to rebuild I haven't found one in the yard yet.
Jeff