Error message on console when using the mechanic of armor stand

Describe the bug
I've created a skill with armor stand mechanics. With the following setting, everything has worked fine but with the spam of error messages in the console. I have no clue on why it happens, but preliminarily I think it is related to the function of the following player maybe.

Expected behavior
Probably there should have no effect on the skill effect, but only the console.

Screenshots

Desktop (please complete the following information):

• OS: Windows10
• Browser chrome

I'm running my server with Yatopia 1.16.5 and Java15.