I have a similar issue after upgrading to 6.43.1. I have a script running at startup from the scheduler and now my log is full of errors.
/system scheduler
add disabled=no interval=10m name=Schedule1 on-event=Script1 policy=read,write start-time=startup
The above schedule configuration worked with RouterOS 6.42.x.
/system scheduler
add disabled=no interval=10m name=Schedule1 on-event=Script1 policy=ftp,reboot,read,write,policy,test,password,sniff,sensitive,romon start-time=startup
I changed the permission to get rid of the following error message. I'm not sure what caused the problem.
00:57:00 script,error could not run script Script1: not enough permissions
Edit: Obviously, the policy must match each other in both the scheduler and the script.