Transition screen - Value of required field (Multi Select Custom Field) is reset if value contains "<", or ">"

When dragging & dropping Card on task board screen, the value of required field is reset like it was never filled out, and the value has to be re-entered.

The required field is set in JIRA workflow - validator, with JIRA suite utilities plugin. The problem happens with Multi Select Custom Field that consists of "<", or ">" as it's value.