parsed result has changed after extend customParseFormat

**Describe the bug**
A clear and concise description of what the bug is.

const dayjs = require("dayjs");
var customParseFormat = require('dayjs/plugin/customParseFormat')

console.log(dayjs("20230406121212", "yyyyMMddHHmmss").format("YYYY MM DD HH:mm:ss")); // 2023 04 06 12:12:12

// long long script ....

dayjs.extend(customParseFormat)

console.log(dayjs("20230406121212", "yyyyMMddHHmmss").format("YYYY MM DD HH:mm:ss")); // 2024 08 01 23:04:06

result has changed after extend plugin

**Expected behavior**
A clear and concise description of what you expected to happen.

second one should be parsed well or, first should't be parsed well from first time
i thought first value is fine, but after some day i added that plugin nobody know that value is broken..

**Information**
- Day.js Version 1.11.5
- OS: window
- Browser chrome
- Time zone: [e.g. GMT-07:00 DST (Pacific Daylight Time)]