
What OS?
What version of Java?
What config changes?
Can you provide ZAP's log? (https://www.zaproxy.org/faq/how-do-you-configure-zap-logging/)
My OS is window 10
Java version:

Config change: I change the port number

This is my zap log
zap.log
As workaround select a default category in the Fuzzer options panel, that should allow to save the options.
Thank you for your help.