I am trying to update my theme, but each time I upload the CSS, or images etc, the site either loeses all styles, or I get this error:

OW Debug - ExceptionMessage:Can't find master page `'.html_document.'` !File:/home/mounts/home/r/domain/web/ow_core/theme_manager.phpLine:230Trace:#0 /home/mounts/home/r/domain/web/ow_core/application.php(432): OW_ThemeManager->getMasterPageTemplate('html_document') #1 /home/mounts/home/r/domain/web/ow_core/application.php(186): OW_Application->newHtmlDocument() #2 /home/mounts/home/r/domain/web/index.php(43): OW_Application->init() #3 {main}Type:InvalidArgumentException

Then after a while/a few refreshes, it comes back again.

What would cause this?

Do I need to clear cache or something each time?

Thanks