ABS Sensor issue ?

So when I first start my car and drive it, its ok. The first time I apply the brakes the abs click in and the pedal pulsates. As if the cars wheels are sliding. Also the speedo is all over the place. It will happen once overtime I drive sand then its fine. Recently I was issued a recall for this issue from VW, but when I went to the dealer, they told me if they fix it it generates another issue. When it happens the ABS and traction light are solid, but soon turn off. The only action i have taken so far is cleaning the two front ABS sensors. they were a pain to get out as they were all gunked up. one cracked but still is intact and works. The only thing I haven't done is clean the rears.

So has anyone have this happen and what was the issue. Any insight helps

I drive a 2009 GTI. Everything revolving the the brakes is factory.