Ok, the main thing is that users were using default weapons this time. And interesting thing was that this error never appeared before 1.26

Could you explain how this check works on the client? Is it check only your player with IK animation or it also could check each player in a radius of loading? Also if weapon could be in Playerbase npc?
Also could you give more information what item class or any info about the wrong weapon?

In T186034#2696445, @sysrover wrote:

Ok, the main thing is that users were using default weapons this time. And interesting thing was that this error never appeared before 1.26

Could you explain how this check works on the client? Is it check only your player with IK animation or it also could check each player in a radius of loading? Also if weapon could be in Playerbase npc?
Also could you give more information what item class or any info about the wrong weapon?

This will require deeper investigation from the dev team. Unfortunately I cannot provide any estimates as to when this could be done due to current internal priorities.
Regards,
Geez

Thank you mr Geez for your help.
I hope dev team will find the way to give proper errors to find out what to fix.
As for now, I blocked part of code in vanilla code that could probably cause this and this wold help until the dev team finds the way.