The "white salts" are the Potassium Chloride (KCL). They can come from the storage solution in the cap or the inner reference solution in the probe. The KCL solution tends to crystalize once it comes in contact with air. They are non-hazardous substances.
If you see some "white salts" leaked out of the pH probe, that’s the reference solution inside the probe. It is NOT a sign of any defective issue. It is a normal situation when the probe is stored dry for a period of time. It actually proves the junction of the probe is working well. Users can simply rinse the probe in distilled water to remove the solids and keep using the tester as usual.
If you see the "white salts" come outside the storage cap (eg. PH60S), it is from the 3M KCL storage solution in the cap. Sometimes traveling from place to place the storage cap can loosen up and some of the KCL could leak out. In most cases, the meter would not have any problem because of that. What you can do is just rinse out and wipe them off with a tissue and keep the spear probe stored in the solution. It is a necessity to always store the spear pH probe in the KCL solution when not in use because the probe can be permanently damaged if stored dry.
There is a very small chance that your meter could be damaged, as the only way it is possible is if the KCL got inside the meter and soaked the circuit board. The best way to check for this is to unscrew the probe from the meter and turn the probe upside down to see if any liquids are running into the circuit board. If this happens you should call the Apera Instruments Customer Service (614) 285-3080 or email firstname.lastname@example.org and we can help you solve the problem.