Cannot execute query with script

[Amitlevizky3]

I'm trying to merge the payload from a consumer with an existing document in my Elasticsearch index using elastic4s 7.17.2. However, when I execute the query with the provided script, I'm getting an error from Elasticsearch:

[
{
"itemId" : 0,
"id" : "123456",
"index" : "myindex",
"type" : "_doc",
"version" : 0,
"forcedRefresh" : false,
"seqNo" : 0,
"primaryTerm" : 0,
"found" : false,
"created" : false,
"result" : null,
"status" : 400,
"error" : {
"type" : "illegal_argument_exception",
"reason" : "failed to execute script",
"index_uuid" : null,
"shard" : 0,
"index" : null,
"caused_by" : {
"type" : "script_exception",
"reason" : "compile error"
}
},
"shards" : null,
"get" : null
}
]

Here is my code (Scala - compiled succesfully):

override val request: UpdateRequest = {
  val retryCount = 5
  val mergeScript =
    """
      |def merge(s, t) {
      |  if (s == null) {
      |    return t
      |  }
      |  if (!(t instanceof Map)) {
      |    return s
      |  }
      |
      |  for (entry in t.entrySet()) {
      |    s[entry.key] = merge(s[entry.key], entry.value)
      |  }
      |
      |  return s
      |}
      |
      |ctx._source = merge(ctx._source, params)
      |""".stripMargin

  updateById(index, id)
    .retryOnConflict(retryCount)
    .script(
      Script(mergeScript).params(Map("param1" -> "100", "param2" -> "5"))
    )
}

Do you happen to know what could be the issue here?

I'm using elastic4s 7.17.2

I've tried to play a little bit with the syntax and to search in elastic4s repo but did not find any solution.