Problem write access during import

-- HikaShop version -- : 2.4.0
-- Joomla version -- : 3.4.2
-- PHP version -- : 5.5

Hi.

I have setup our local server running the hikashop to call the cron job url every 15 minutes to import products. The cron job calls the Products Cron Update Plugin.

When the site is accessed during the import, there are errormessages claiming that the images/com_hikashop/upload/thumbnails/0x200f directory isn't writeable.

Once the import has finished, the errormessages disappear.

I have checked the access rights, and the directory is writeable (linux).

Have you any idea, what could cause this?

Thanks. I have turned off the 'force size' setting. We will see how things goes.