Unable to submit application under OCI Miscellaneous service

Hi
I am trying to submit an application under the OCI Miscellaneous service as a new passport has been issued.
After entering all the details correctly, the form throws an error saying
GBR, is not of Valid Size
GBR, is not a valid Mission Code
GBRB, is not of Valid Size
GBRB, is not a valid Mission Code

I have chosen the right dropdown values and none of the fields in that form had a value of GBR.
Even in OCI card, the nationality shows as GBR.
Has anyone faced this issue. Please help.