Is there a maximum length of a string?

I ask, because I have a json object, which I am publishing via MQTT, and I'm getting a run time error "arguments too long", which is where I convert the json to a string (prior to ListofByte).

Depending on how long the strings in the json are, I get the error, or not. The magic number seems to be around 280 characters.

I'm working around it by splitting the strings into two json objects, and publishing both of them (which works).

What are the limitations?

Thanks,