Comparing two curly-braced Expression values inside a Condition looking for change generates an error

[kapstaad]

Expression1: HarmonyOFF = -1
Expression2: HarmonyTV = 1234567
Expression3: tonumber(getstate( "Harmony Control", "urn:rboer-com:serviceId:Harmony1", "CurrentActivityID" ))

Condition TVON: Expression Value HarmonyMode changes from {HarmonyOFF} to {HarmonyTV} (ignore case)

Result:
2021-03-06 16:02:08: TROUBLE: Evaluation error in "HarmonyOFF},{HarmonyTV": [luaxp]Invalid operator at 11

[kapstaad]

Additional info: changing either (or both) of the curly-braced Expressions within the condition to 'hard' numbers resolves the TROUBLE warning. The error seems to only occur if the "changes-from" comparator is asked to look for a change from one curly-braced Expression to another.