I've been using Salifert for over 10 years. I can't recall any issues at all with their test kits.
I also have a Hanna alk checker and Hanna ulr phosphorus checker. The phosphorus checker is working well for me.
I'm having a hard time trusting the alk checker though. My last batch of reagent is reading 1.2dkh lower than my Salifert kit. Since I've used Salifert for so long, I go by that reading over the Hanna.