Depends on what changed. Did the max. speed/acceleration in firmware settings change? Or did the z rods run dry and now have more friction to motor now stalls with old values? Rods not parallel any more adding friction? Many motor drivers also set motor current with a poti. Did it change position? Guess you did not open box to change it. Standrad is that printer it self limits speed/acceleration so hosts can send higher speeds then possible and it still works, becase firmware reduces to allowed values.
You can also try reducing acceleration/max speed. How depends on printer firmware. Run M115 to query which firmware the printer runs.
