This is spamming the console:

https://gyazo.com/d4cc58ece9c128bc8b0d7475c561d877

I am using the latest dev build from the jenkins website.

Getting this aswell
Paper 1.13 Latest Dev version.

I can confirm I get this as well using Paper #522, https://pastebin.com/7DF7HP30
Setting old-armor-strength enabled to false stops the error from occurring until an update arrives which will fix the problem.

@Leomelonseeds @LoXR @darksaid98 Sorry lads, it appears this may be a very simple fix. Can you try test version 33 or greater?

I can confirm I get no errors anymore with the setting, enabled running the latest dev build#33 & paper 525. Thanks for the patch =)