Agolia “restrictSearchableAttributes” does not work with too many searchable attributes

I have a search index (for a b2b webshop) with about 200,000 products. For each product, the customer number of the product is stored per customer in a key-value array (key = customer number, value = article number).

Below an example of an item in my search index

{
  "id": 45782,
  "sku": "12.34.56",
  "title": {
    "nl": "Accu 12V 230Ah Bosch semitractie"
  },
  "brand_id": 184,
  "brand_name": "bosch",
  "customer_references": {
    "101028": "ABC-123",
    "101029": "DDD-34433",
    "101030": "4-243345",
    "101031": "4-33333",
  },
  "category_ids": [
    5100,
    5091,
    5070,
    5000
  ]
}

I have added all these fields to the “searchableAttributes” setting of the index and now I want to indicate per query in which fields can be searched using the restrictSearchableAttributes parameter (because I only want to search in the field corresponding with the customer number of the logged in user). This works fine if I don’t have more than 64 searchable attributes, but in my case I have hundreds of different customer numbers. It still works fine if I add one of the first 64 searchable attributes to the restrictSearchableAttributes parameter, but when I add searchable attribute number 65 or higher to the restrictSearchableAttributes parameter I get no results at all. Anyone an idea how I can fix this?