Makita 40V Max Brushless AWS HR001GZ

Upgraded from MAKITA 18v to the 40V XGT platform 12months ago primarily to get a better H/Duty drill than the awful DPH486 drill. All the 40V tools have performed faultlessly except for the HR001G 28mm Rotary Hammer. First time I used it for a job drilling 75 holes with 12mm concrete bit 100mm deep in asphalt and it would stop after approx 5 holes. Also the SDS drill bits would pull out of the chuck as soon as I pulled up hard when stuck. My batteries were in good condition, I tried 2 different batteries both 4AH and both had 3 bars charge with same result, about 5 holes and it would just stop. After sufficient break to cool down it would run again but not exactly conducive to a productive work day. I resorted back to my old 18V SDS and it sailed through the remaining 75 holes without breaking a sweat. I sent the tool to MAKITA for repairs, it was returned to me stating nothing was wrong with the tool so I sent it away again. I have now received it back from MAKITA and again advised nothing is wrong with it and I should use a new battery. These 40V batteries are definitely not cheap, mine are all 12 months old and hold their charge. They also work fine in my other XGT tools. My dilemma now is I have a tool that retails between $550-$650 without the cost of the battery that can’t handle more than 5x12mm holes. It could be that I just got a Dud but it raises the question is the MAKITA XGT platform actually and upgrade in quality from the 18V, probably not! Is the XGT platform worth the high cost? Not sure but I now doubt it is!