Had the exact same problem with my Hanna stick. Been using it for months, reading 1.026, had some issues and took my water to a LFS for testing, they read 1.029!! Got a refractometer after that. Even after calibration the Hanna still reads 0.002 lower than refractometer
I am highly recommending the Tropic Marin Hydrometer for exactly the reasons you pointed out. Under normal temperatures, the Hydrometer can't be wrong, I use it to calibrate my Hanna.
Very nice, I'd been looking at those floaties and other salt checkers for a while, watching you go through all that is enough to get it out of my system 🙂 I'm not a fan of taking refractometer readings w/o my glasses... my cheesy cheep salt probe has matched the refractometer for a year now, I'm almost afraid to recalibrate them🙃
You should put the Hanna calibration fluid in your sump to match the temp first then calibrate outside. Also cleaned the sensor too. Then you should be on point.
