As a part of v2.3.0 update, extension structure undergone serious changes.
As a result, if an update from older version to v2.3.0 or above will be performed 'as is' without using Composer, some loose files will persist in extension folder.
The extension may misbehave or cease to work because of these redundant files.
To resolve it:
Composer will clean [Magento root folder]/vendor/amasty/feed automatically before installing the update, effectively, removing the difficulity's cause automatically.
Reference for Composer usage is available here.