Steven Zahm@ Rolf
There’s nothing I can do about this. The htaccess with this rule will prevent anything from loading in the uploads folder that is not specifically uploaded using the WordPress Media Manager. This rule will actually break quite a few plugins because this is the folder as a matter of best practices where uploads should be saved.
I too use SiteGround so I’m fairly certain this is not a rule being auto applied by them. A quick Google shows that this is actually being added by the User Access Manager plugin. My guess anytime you upgrade that plugin, it checks the uploads folder and if it is missing adds it again.
There is an “Lock Files” option on the plugin’s settings page not to add this file. Disable this option and you should not longer have this issue. If you wish to protect the uploads folder, there are far better rules you could use which are not as restrictive. One rule I use is I prohibit the access to php files and only allow access to a defined set file types such as various image and text file formats.
I hope this helps!