This article explains how to resolve Adjustment error:
Action incomplete: Other users may have modified stock levels.
ONE OR MORE ITEMS seems to have changed quantity after count;
Try turning OFF USE UNITS when making fractional adjustments.
Please refresh adjustment and try again.
This is a known issue when user turned on fractional items after the item has been used etc.
Login to WMS as superuser
Open Tools > Preferences > Security Tab
Turn OFF setting for below
4. Restart WMS and try again