Like John asked, is it hitting the limit switch or end of travel?
What I know is that the 50A has a weird ass homing sequence.
Even though it remembers the position from last power down, it still wants a homing after power up.
So, what it does is it looks at the position it remembers from power down and starts traveling towards home.
Let's say it remembers 5.0000 from home, it wants to travel ABOUT 5" worth towards home, plus/minus some.
Now, let's say that while the power was shut off, someone manually bumped the axis and it moved by .1 in one direction.
When the mach. is powered up, it still remembers 5.0" and wants to travel that distance towards home.
BUT!
Since the axis was moved by .1 without the control knowing it, the travel will take either less or more distance to hit the switch.
So, if the nudge was in the -X direction, then the machine will hit the switch sooner than it expects it and alarms out with the overtravel.
If OTOH the nudge was in the +X direction, then it'll come up with something like a "No Home X found" error.
So based on that, I'd suggest you power off the machine and manually move the axis ( turn the ballscrew, you can reach it from the bottom ) towards +X so it needs to move a bit more to get home.
I know that these ballscrews are pretty fine pitch, it is still quite easily moved when no power is applied.