@param.array throws INVALID_PARAMETER_VALUE:must be string if more than 20 elements are sent

Describe the bug

Hello, I have an LB application running correctly in prod for couple years. I used LB4 CLI update command in my test environment, and now I'm getting INVALID_PARAMETER_VALUE:must be string error code for a REST request -that works fine in prod- when sending more than 20 values on a @param.array query param.
I assume its handled by @loopback/rest. If so, prod has v12 and my test environment v15.0.9.

1.- How to reproduce:
Having the following code in my controller:

@param({
      name: 'vendorNumbers', in: 'query', schema: { type: 'array', items: { type: 'string' } }
    }) vendorNumbers: string[],`

and calling

http://{url}/queries/selectShipments?vendorNumbers=1000294151&vendorNumbers=1000486268&vendorNumbers=1000107612&vendorNumbers=1000433151&vendorNumbers=1000353795&vendorNumbers=1000059059&vendorNumbers=1000046043&vendorNumbers=1000328740&vendorNumbers=1000353800&vendorNumbers=1000254679&vendorNumbers=1000468101&vendorNumbers=1000493680&vendorNumbers=1000483049&vendorNumbers=1000479051&vendorNumbers=1000346467&vendorNumbers=1000478186&vendorNumbers=1000428780&vendorNumbers=1000064789&vendorNumbers=1000411703&vendorNumbers=1000120574&vendorNumbers=1000056801

I get the following error:

{
	"error": {
		"statusCode": 400,
		"name": "BadRequestError",
		"message": "Invalid data [{\"0\":\"1000294151\",\"1\":\"1000486268\",\"2\":\"1000107612\",\"3\":\"1000433151\",\"4\":\"1000353795\",\"5\":\"1000059059\",\"6\":\"1000046043\",\"7\":\"1000328740\",\"8\":\"1000353800\",\"9\":\"1000254679\",\"10\":\"1000468101\",\"11\":\"1000493680\",\"12\":\"1000483049\",\"13\":\"1000479051\",\"14\":\"1000346467\",\"15\":\"1000478186\",\"16\":\"1000428780\",\"17\":\"1000064789\",\"18\":\"1000411703\",\"19\":\"1000120574\",\"20\":\"1000056801\"}] for parameter \"vendorNumbers\".",
		"code": "INVALID_PARAMETER_VALUE",
		"details": [
			{
				"path": "/0",
				"code": "type",
				"message": "must be string",
				"info": {
					"type": "string"
				}
			}
		]
	}
}

Have in mind that:

• if I send less than 20, works fine.
• it is not related to query length nor number of other params, cause I already tried with different lengths and number of 'other' parameters.
• If I add maxItems of 30, I still get INVALID_PARAMETER_VALUE:must be string when sending more than 20 values.
• During one of my tests, I set maxItems at 10, and the error changed to INVALID_PARAMETER_VALUE:must NOT have more than 10 items

Thanks

Logs

Additional information

No response

Reproduction

Inizia dal percorso di parsing e convalida dei parametri di query di @loopback/rest, confrontando il comportamento segnalato in v12 con v15.0.9. Riproduci la richiesta usando i 21 valori vendorNumbers ripetuti mostrati, quindi verifica perché i valori oltre 20 vengono gestiti in modo errato mentre la convalida di maxItems continua a funzionare. Il lavoro è completato quando gli array con più di 20 elementi vengono convalidati come stringhe senza regressioni negli errori maxItems.