What is the ruling on swallowing saliva when there is a strange, semi-permanent taste in the mouth, whether one is fasting or not?

There is no harm in swallowing saliva that has a taste, whether one is fasting or not, because preventing it entails obvious hardship. Swallowing saliva in general does not break the fast by scholarly consensus if it is customary, because it is difficult to guard against, and the taste does not affect the fast as long as it descends almost constantly and is difficult to guard against. One should be cautious of obsessive whispering (waswasah) regarding this.