Missing variable substitution in FILTER

[lroffia]

"IRRIGATION_REQUEST_BY_DAY": {
"sparql": "SELECT * FROM <http://swamp-project.org/cbec/irrigation> WHERE {?irr rdf:type swamp:IrrigationRequest ; time:inXSDDateTimeStamp ?timestamp ; swamp:issuedBy swamp:CBEC ; swamp:hasCurrentStatus swamp:Scheduled ; swamp:requestNumber ?requestNumber ; swamp:reservationNumber ?reservationNumber ; swamp:hasField ?fieldUri ; swamp:hasStatus ?status . ?status time:inXSDDateTimeStamp ?stime ; swamp:requestStatus ?reqStatus . FILTER(contains(?timestamp,?day))}",
			"forcedBindings": {
				"day": {
					"type": "literal",
					"value": "2020-07-14"
				}
			}
		}

It seems like "?day" is not substituted within the query.

[relu91]

It seems that the query bench correctly substitutes the variable. See here. Can you provide more context? i.e. client version, a small snippet to reproduce the issue, etc. ?