"POST’ing Search Template as REST API causes Elastic to fail on start"

[majunzhe]

I POST an search template using REST API, and it works as excepted.
But when I restart the es after registering the template, it throws an exception.
Origin question Link https://discuss.elastic.co/t/posting-search-template-as-rest-api-causes-elastic-to-fail-on-start/82552

I am also getting the same exception.

[jasontedor]

I think there's indeed a real issue here starting in 5.3.0, maybe related to #22206?