This is by the same author that wrote Lynchpin - which, if you haven't read, is an amazing time travel fix it (it was recced here, which is how I found it).

Rotten Work (63907 words) by ShanaStoryteller
Chapters: 8/8
Fandom: 陈情令 | The Untamed (TV), 魔道祖师 - 墨香铜臭 | Módào Zǔshī - Mòxiāng Tóngxiù
Rating: Not Rated
Warnings: Creator Chose Not To Use Archive Warnings
Relationships: Lán Zhàn | Lán Wàngjī/Wèi Yīng | Wèi Wúxiàn, Jīn Líng | Jīn Rúlán & Wèi Yīng | Wèi Wúxiàn
Characters: Wei Ying | Wei Wuxian, Lan Yuan | Lan Sizhui, Lan Zhan | Lan Wangji, Jiang Cheng | Jiang Wanyin, Luo "Mian Mian" Qingyang, Jin Ling | Jin Rulan, Lan Jingyi
Additional Tags: Post-Canon, Protective Wèi Yīng | Wèi Wúxiàn, Protective Jīn Líng | Jīn Rúlán, POV Jīn Líng | Jīn Rúlán, Jiāng Chéng | Jiāng Wǎnyín & Wèi Yīng | Wèi Wúxiàn Reconciliation, eventually, Reluctant Matchmaker Jin Ling, this kid is doing his best, Pre-Jīn Líng | Jīn Rúlán/Lán Jǐngyí if you squint
Summary:

Jin Ling hadn’t thought to keep track of Wei Wuxian.

Clearly that had been a mistake.