Applying suggestions failing with 400 on PUT https://gitlab.com/api/v4/suggestions/.../apply

Summary

Applying suggestions failing with 404 on PUT https://gitlab.com/api/v4/suggestions/.../apply

Steps to reproduce

• Have a recent MR with suggestions applied already
• Create and apply suggestion
• Get Something went wrong while applying the suggestion. Please try again.
• Open up chrome dev tools

Example Project

• gitlab-com/www-gitlab-com!69464 (diffs, comment 495442973)

Relevant logs and/or screenshots

xhr.js:184 PUT https://gitlab.com/api/v4/suggestions/781317/apply 400
(anonymous) @ xhr.js:184
JgJM.t.exports @ xhr.js:13
Iu5f.t.exports @ dispatchRequest.js:50
Promise.then (async)
SKMx.c.request @ Axios.js:61
SKMx.r.forEach.c.<computed> @ Axios.js:86
(anonymous) @ bind.js:9
applySuggestion @ api.js:448
Ae @ actions.js:570
(anonymous) @ vuex.esm.js:851
f.dispatch @ vuex.esm.js:516
dispatch @ vuex.esm.js:406
E.forEach.n.<computed> @ vuex.esm.js:1064
applySuggestion @ note_body.vue:105
zt @ vue.esm.js:1863
n @ vue.esm.js:2188
zt @ vue.esm.js:1863
t.$emit @ vue.esm.js:3897
(anonymous) @ suggestions.vue:124
zt @ vue.esm.js:1863
t.$emit @ vue.esm.js:3897
applySuggestion @ suggestion_diff.vue:55
zt @ vue.esm.js:1863
n @ vue.esm.js:2188
zt @ vue.esm.js:1863
t.$emit @ vue.esm.js:3897
applySuggestion @ suggestion_diff_header.vue:91
zt @ vue.esm.js:1863
n @ vue.esm.js:2188
zt @ vue.esm.js:1863
n @ vue.esm.js:2184
i._wrapper @ vue.esm.js:7565