Dart client api errors

occasionally I encounter errors in production when calling the api method on the Dart ServiceStack client for Flutter in version 3.0.0.
I haven’t been able to identify a pattern, but I have stack trace from Sentry logs:

_TypeError: type '_Map<String?, String?>' is not a subtype of type 'Map<String, String>?' in type cast
  File "utils.dart", line 190, in createUri
  File "client.dart", line 517, in JsonServiceClient.createRequest
  File "client.dart", line 425, in JsonServiceClient.sendRequest
  File "client.dart", line 219, in JsonServiceClient.fetch
  File "client.dart", line 198, in JsonServiceClient.api

Example code I am using:

Future<List<ReportDto>> getReports() async {
    final req = GetOpenReports(userId: ioc<AuthService>().userId.value);
    final res = await client.api(req);
    if (res.succeeded) {
      final reports = (res.response?.results ?? []);
      return reports;
    } else {
      showErrorDialog(res.errorMessage ?? 'An error occurred');
      return [];

Any advice?

would need to be able to repro to identify, are you saying it only occasionally happens, i.e. the same code will sometimes fail with this _TypeError?

Yes, it seems that the same code sometimes throws errors, but not 100% sure about that.
I will try to repro.