UV White drops

We've had a problem with white for a while.
When printing in white, immediately after cleaning it prints well. Then at the second or third job, take out a few drops of white, as if spraying.
Immediately after cleaning, the first job is very ok.
I understood from the service that it would be a problem with temperature, humidity and electrostatic charge.
I put a humidifier, I have over 50-55% humidity, I increased the heat, but it still does.
From what could it be?
Until about 5-6 months ago, it hasn't been done, being kept in the same place for about 3 years.
I'm attaching some pictures.
Thanks