类型错误：无法设置未定义的属性“旧”

Question

我在打字稿中有这个函数，我在其中为我收到的对象的属性赋值。

async buildFactsDocument(ruleId: string, updateDocument: UpdateObject) {
        let facts: Array<string> = await this.getFacts(ruleId);
        type FactKeys = keyof Fact;

        await Promise.all(facts.map(async( fact: string )=>{
            let value = await this.getFactsValues(ruleId, fact);

            (((updateDocument as {update: Update}).update).fact![fact as FactKeys] as Values).old = value;
            (((updateDocument as {update: Update}).update).fact![fact as FactKeys] as Values).new = value;
        }));
        return updateDocument;
    };

有问题的对象是这个，我正在给里面的属性添加值：

let updateObject: UpdateObject = {
    
        update: {
            name: {
                old: null,
                new: null
            },
            priority: {
                old: null,
                new: null,
            },
            engine: {
                old: null,
                new: null
            },
            fact: {
                brand: {
                    old: null,
                    new: null
                },
                model: {
                    old: null,
                    new: null
                },
                version: {
                    old: null,
                    new: null
                },
                year: {
                    old: null,
                    new: null
                },
                km: {
                    old: null,
                    new: null
                },
                color: {
                    old: null,
                    new: null
                },
                source: {
                    old: null,
                    new: null
                },

            },
            adjustment: {
                old: null,
                new: null
            }
        },
        create: {
            conditions: null,
            recipe: null
        },
        delete: {
            conditions: null,
            recipe: null
        },
        
    
};

对象是在这个接口结构中声明的：

export interface UpdateObject {
    update?: Update;
    create?: CreateDelete;
    delete?: CreateDelete;
}

export interface Update {
    name?: Values;
    priority?: Values;
    engine?: Values;
    fact?: Fact;
    adjustment?: Values;
}

export interface Fact {
    brand?: Values;
    model?: Values;
    version?: Values;
    year?: Values;
    km?: Values;
    color?: Values;
    source?: Values;
}

export interface Values {
    old?: any;
    new?: any;
}

export interface CreateDelete {
    conditions?: any;
    recipe?: any;
}

我有一个问题，在某些情况下，调用此函数时出现错误：无法设置未定义的属性“旧”。 this.getFacts 函数返回的事实是动态的，可能会改变。错误是因为这个吗？我没有找到错误的确切原因，因为在某些情况下它可以工作，而在其他情况下它会给出错误。