Swagger UI, array of objects in multipart/form-data problem

I got problem similar to this one Link, but I can't find a solution. Swagger has problems uploading the list of objects. The API reads the list of passed InterestDto's as empty. The problem only occurs in swagger, a properly constructed query in Postman works. This particular snippet deals with request with multipart/form-data, but the same problem occurs elsewhere when using query. Here's my attempt at dealing with it, which unfortunately doesn't work. It gives an error:

System.Collections.Generic.KeyNotFoundException
  HResult=0x80131577
  Message=The given key 'Interests' was not present in the dictionary.
  Source=System.Private.CoreLib
  StackTrace:
   at System.ThrowHelper.ThrowKeyNotFoundException[T](T key)
   at System.Collections.Generic.Dictionary`2.get_Item(TKey key)
   at Flats4us.Helpers.CustomOperationFilter.Apply(OpenApiOperation operation, OperationFilterContext context) in C:\Dane\Projekty\Flats4Us\Flats4us\Flats4us\Helpers\CustomOperationFilter.cs:line 23
   at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.GenerateOperation(ApiDescription apiDescription, SchemaRepository schemaRepository)

AuthController.cs:

[HttpPost("register/Student")]
public async Task<ActionResult<User>> RegisterStudentAsync([FromForm] StudentRegisterDto request)
{
    try
    {
        await _userService.RegisterStudentAsync(request);
        return Ok("Registered successfully");
    }
    catch (Exception ex)
    {
        return BadRequest(ex.Message);
    }
}

UserRegisterDto.cs:

[ModelBinder(BinderType = typeof(MetadataValueModelBinder))]
public class StudentRegisterDto : OwnerStudentRegisterDto
{    
    [...]

    public List<InterestDto> Interests { get; set; }
}

Program.cs:

builder.Services.AddSwaggerGen(options =>
{
    options.OperationFilter<CustomOperationFilter>();
    [...]
}

MetadataValueModelBinder.cs:

public class MetadataValueModelBinder : IModelBinder
{
    public Task BindModelAsync(ModelBindingContext bindingContext)
    {
        if (bindingContext == null)
            throw new ArgumentNullException(nameof(bindingContext));

        var values = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);

        if (values.Length == 0)
            return Task.CompletedTask;
        var options = new JsonSerializerOptions() { PropertyNameCaseInsensitive = true };

        var deserialized = JsonSerializer.Deserialize(values.FirstValue, bindingContext.ModelType, options);

        bindingContext.Result = ModelBindingResult.Success(deserialized);
        return Task.CompletedTask;
    }
}

CustomOperationFilter.cs:

public class CustomOperationFilter : IOperationFilter
{
    public void Apply(OpenApiOperation operation, OperationFilterContext context)
    {

        if (operation.RequestBody != null && operation.RequestBody.Content.TryGetValue("multipart/form-data", out var openApiMediaType))
        {
            var options = new JsonSerializerOptions { WriteIndented = true };

            var array = new OpenApiArray
            {
                new OpenApiString(JsonSerializer.Serialize(new InterestDto {InterestId = 0, Name="string"}, options)),
            };

            openApiMediaType.Schema.Properties["Interests"].Example = array;
        };
    }
}