Steering stabilizers if not correctly positioned will cause the very same issue, even a quarter inch can produce constant drifting to whatever side happens to be off. They can and do come off calibration as well if they are not torqued to specs, this happens frequently since it takes a few attempts to get them dialed in at time of installation.
Many instances steering stabilizers are adjusted by tech alongside roadway or parking lot and they don't always get them torqued properly. Other suggestions above are truly valid as well, but with a Safe-T-Plus steering stabilizer that is where I would start as it is common issue, they work great when properly dialed in.