You are not the only one. I reported this a couple months ago. Hoping they get a fix for it.
Others have stated this exact problem:
In FileMaker Pro 10 for select, delete, and other DBMS specific statement, it doesn't support statement lengths greater than 4096 characters.
There seems to be 2 different issues:
First, the total query length is now limited to 4096. If you run a query which is not an INSERT or UPDATE query, then this is the limitation.
The second case is for INSERT or UPDATE queries. If the total query length is less than 4096, then there is no problem. However, for INSERT or UPDATE queries, it is very likely that the query length will be longer, as long text data could be sent as parameters. In this specific case, we are extracting the text parameters and send them separately from the rest of query. The query without parameters is still limited to the 4096 characters lengths, parameters themselves can be as long as they want. However, we have encountered some limitations coming from the drivers, and they concern the data this time, not the query.
I hope this information helps.