is it normal that the rear outriggers after time can go inside during the load of the pump or in this case we have a problem in check valves or the seal kit

Sounds like you have a problem.. Thats not normal

It's either the holding valve on the top (piston) side of the outrigger, or the seals on the internal piston bypassing to the rod side and blowing past the holding valve due to over pressure on the rod/ low side. 

I haven't run into a piston seal problem before. If it were me, I'd jack up the truck and then remove the line from the outrigger that supplies the oil to lift the truck and cap the outrigger at the holding valve. Put some load on the outrigger. If it still drops, you need piston seals. If it stays you need a holding valve. 

I think this is correct, but get a second opinion first. 

 Also This pump is 2011 model We had older pumps and They dont have The Same problem