v6.33.3 simple Script seems to kill Firewall

We have a long script for managing our Firewall-Rules/Chains… at the beginning we are marking all rules as “old”, add all rules again and remove all “old”-Rules. This worked pretty well past the previous releases. In 6.33.3 any significant change happend :frowning:

processing these two lines kills reproducible any of my ccr-routers:

/ip firewall filter 
set comment="OLD" [/ip firewall filter find]

in the log i can see, a few rules where changed - the script seems to stop work (is not finishing).
any ideas? is this a known bug in the current release or a change?