All shards failed - 400 happens on certain indexes

Hi,
A bit of a background - We are using ElasticSearch with index per client for search engine.
Now we let the user have several types of search terms that one of them is "search by id" where we focus the search to certain fields.
ElasticSearch v7.4

We have the following query for that:
{ "query": { "bool": { "must": [ { "multi_match": { "query": <ID>, "fields": [ "Id", "*Id*", "*id*" ], "type": "best_fields" } } ] } } }

Now the query above works for most cases we use it.
Recently we encounter an index where it fails with all shards fails with status code 400, we did some trail and error and found that if we remove from "fields" the element "id" the query will work.
Now where we found that issue is a rather small index with about 60 documents and size of less than 1 MB inside which none of them actually have a field with *id*.
The index health is green and I have 3 primary shards and 1 replica set for it

Can someone shade some light on this behavior?
Thanks in advance