There may be truncation and roundoff errors if AirWrench is used to convert English units to Metric units, and back to English units. This is not considered a bug, and there is no solution for it.  That's simply the way things work.

When AirWrench converts feet (to the nearest thousandth) to meters (to the nearest millimeter) some accuracy may be lost through truncation. When converting back to feet, the data truncated on the conversion to meters is rounded to the nearest thousandth.

The difference in dimensions won't matter as far as any flight model is concerned, but these small discrepancies can be disconcerting (and annoying) to find that 8.000 ft converts to 2.438 meters (2.4384 truncated to 2.438), which converts back to 7.999 ft (7.998664 rounded to 7.999).  The best advice is to work exclusively in English units or Metric units.