I noticed some of my nagami kumquat fruit is squishy. Most are still firm. Seems to be worse near the top exposed areas. They are just now yellowing up.

Any luck on your question? I'm sorry I could be of no help. I grow mine indoors during the bad weather. It does make sense though that frost damaged fruits would go mushy, altering the texture. I know with our plums, we had an early frost and they went mushy. edible.. but just a very wrong texture. turned them into jam