A January or February birthday can receive different year stems in different chart tools. Gregorian New Year, Lunar New Year, and Start of Spring are separate boundaries. A birth between the latter two is especially sensitive to the convention used.
Check the calculation convention
Some Zi Wei Dou Shu methods follow the lunar-year boundary. Other configurations use Start of Spring. If a method uses the solar term, its exact time must come from that year's calendar; a fixed date is not enough near the boundary.
The birth-year stem determines the natal transformation table. Changing it may also change stars calculated from the year. Two charts can therefore differ for a traceable reason rather than because one randomly assigned different stars.
Compare one setting at a time
Keep the birth date, time, and other options unchanged while comparing the year setting. Record the displayed lunar date, year stem, and transformations. Do not combine favorable statements from both charts into one reading.
If you compare candidate charts against past events, save the candidates before discussing the events and retain the mismatches. A complete screenshot should include the calculation settings as well as the twelve palaces. Establishing which chart was actually calculated comes before interpreting it.