I removed the grip and had no problem due to cold temperature (This seems to indicate that the glue of the grip could be responsible). Then, I put on the footpad the foam "Traction Pad" from ProRide. For this, I left the board and the pad outside in the cold for a moment, before sticking the pad. Since then, I did not have any "ghost rider" problem. To conclude, I had problems with classic skate grip tape from Vicious and Black Diamond, and now that I have ProRide pads everything is fine.

My neighborhood tire store filled my OW tire with nitrogen for free! Larger molecules = no more loss of pressure. Been 4 months now and holding steady.