Can't encrypt values that are numeric only characters

[Replica-]

Running
sls encrypt -n XXXX_PASSWD -v 1234567 -k 9999-9999-9999-9999
Always results in
Serverless: UnknownError: 413

Alternatively, running
sls encrypt -n XXXX_PASSWD -v a1234567 -k 9999-9999-9999-9999
Results in success

Unfortunately, my XXXX_PASSWD is all Numeric characters. I would hazard a guess here - at some point the value is being interpreted as Number and not a String value.

[Replica-]

Just noticed deprecated. Posted in wrong area