Since upgrading to the latest LTS (and after multiple plugin updates) jobs that use variables like ${variable} instead of $variable can't be saved anymore.

Clicking save will result in a ERR_CONNECTION_RESET.

Also, unchecking "Use Groovy Sandbox" will result in a "An internal error occured during form validation (HTTP 0)" underneath the pipeline script text box. (See images)

Changing variables to $variable lets the jobs be saved.

Existing jobs with the ${variable} syntax are still able to run but not modified.