I have tested what is the effect when A axis is physically blocked to check if stalling is / can be caused by external load.
When A axis is blocked effect is very different than when motor stalls during run. In case of blocked axis there is more like "clacking" sound and when motor stalls during run test it buzzes (sound closer to buzzing of 3 phase electric motor if you block it) . This sounds are very different.
So my suspicion is it is not external mechanical resistance/load that is causing motor to stall.