On one D7 migration (not another from same time)...

Editing user profile, results in user picture disappearing. Upon resubmitting picture, get Notice:

Notice: Trying to access array offset on value of type bool in UserStorageController->preSave() (line 409 of /PATH_TO/public_html/core/modules/user/user.entity.inc).

Then this, but saves user picture anyway, with no more notices / errors

File temporary://FILE_NAME.jpg (/PATH_TO/tmp/FILE_NAME.jpg) could not be copied because it does not exist.

Same if Temporary directory = ../tmp or /tmp (first usally used).