On the basis that I think the surface area of the wick isn’t sufficient for dense root masses I did an experiment to create my own wick that exposed more of the root mass to it.
I’ve ordered some longer wicks from Amazon but being impatient I decide to make one out of cotton string. I took out the original wick and threaded four lengths of cotton kitchen string up through the soil at different angles from the contact point to the hole. 3 hours after putting it back in the water it is now as wet as my other plants which aren’t root bound. About 1/4 of my plants have this issue.
I’ll update to see if this causes any problems, given it is cotton I suspect it will rot over time. I’m also going to look at longer wicks which I found on amazon.
a very dry plant
strings to replace wick
making a hole
a crochet needle worked well as a needle to thread it through the soil
four total strings at different angles to get good contact with the soil/roots
twisted them round and threaded them through the base of the pot with the crochet needle again