Error in data.table::fread(cmd = fread_cmd, select = sampler_diagnostics, : R character strings are limited to 2^31-1 bytes

[JCruk]

I am running a model with some out of sample predictions in generated quantities.

When I sample from the model without the out of sample predictions, everything is fine and runs as expected.

When I include the predictions, I get the following error:

Error in data.table::fread(cmd = fread_cmd, select = sampler_diagnostics, : R character strings are limited to 2^31-1 bytes

Am I correct that this suggests a very long string is being generated somewhere? Is it possible to work around?