Answer
This is a specific, confirmed performance regression that has historically affected Context Substitution Variables (CSVs) generally in Lobbies on certain update levels — not something specific to your own lobby configuration. If you see this exact symptom pattern (a CSV-based parameter causing slow/stalled loading, resolved by typing the literal value instead), it's worth checking current release notes or raising a case referencing Context Substitution Variable performance in Lobbies, since this was a known, tracked issue addressed in a subsequent update on at least one release track.