Moving all the related assets to another folder at once leads to reference lost in the contents browser.

Moving all the related assets into another folder leads to reference lost.
This can be tested out using ShooterGame project.

Also you can find materials in the skeletal mesh lost its texture.

This is not reproduced when moving folders separately, i.e.
1) Select Animations, Environment, Sounds then move into ShooterGame folder
2) When 1) is finished, Select Characters folder then move into ShooterGame folder.

Regression? Yes, this is not reproduced in 4.15 version.

1) Create a ShooterGame project from launcher
2) Go to Contents\Animations\TTP_Animations
3) Select Idle, Run_Fwd anim instances
4) Right click, select Asset Actions > Migration.. from context menu
5) Select blank project and migrate.
6) Close editor
7) Open blank project which just received animations and followings.
8) Create a new folder under Contents at the content browser as ShooterGame
9) Select every folders except ShooterGame folder
10) Move selections into ShooterGame folder
11) Right click at Contents folder
12) Select Fix up redirections in the folder from the context menu.
13) Close editor
14) Reopen the blank project
15) Go to Contents\ShooterGame\Animations\TTP_Animations
16) Double click to open existing animations
Expected: The anim instance opens without error
Result: The anim instance lost its skeleton and asking for selecting one.