2626837 - 'isUnicode': Radio group contains an invalid value ''. Valid values are: false|true|

You prepared a parameter file on a single host for ASCS, DB and PAS for distributed system installation in unattended mode - see SAP Note 2230669.
When installation is running in unattended mode, PAS installation is terminated with below error in sapinst_dev.log:

TRACE 2018-03-13 16:44:18.949 (root/sapinst) (startInstallation) [DarkModeDialog.cpp:108] DarkModeDialog::submit()
Front side checks for 'd_nw_askUnicode' returned false:
Checking input element 'isUnicode': Radio group contains an invalid value ''. Valid values are: false|true|

ERROR 2018-03-13 16:44:18.950 (root/sapinst) (startInstallation) [iaxxbjsmod.cpp:83] id=modlib.jslib.caughtException errno=MUT-03025
Caught ESAPinstException in module call: Validator of step '|NW_ABAP_CI|ind|ind|ind|ind|0|0|NW_GetSidFromProfilesPartial|ind|ind|ind|ind|getSid|0|NW_getUnicode|ind|ind|ind|ind|unicode|0|askUnicode' reported an error:
Start SAPinst in interactive mode to solve this problem.

When you scroll up in sapinst_dev.log, following entries appear:

TRACE 2018-03-13 16:44:18.468 (root/sapinst) (startInstallation)
NWInstall.runExecutableForVersion([], [disp+work, msg_server])

TRACE 2018-03-13 16:44:18.469 (root/sapinst) (startInstallation)
NWInstall.runExecutableForVersion() done: none of disp+work, msg_server found in .

WARNING 2018-03-13 16:44:10.537 (root/sapinst) (startInstallation) [iaxxcmsclient.cpp:284] id=wapsmod.ms.MsCommandFailed CIaMsgClient::getProfileValue(UNICODE)
MsGetProfileValue on message server (<ASCS_host>/36<instance_nr>) failed:MSOP_ACCESS_DENIED.

NW_getUnicode.isUnicode Unicode non-Unicode dark , KBA , BC-INS-SWPM , Installation with Software Provisioning Manager , Problem