Strange behaviour of online CMS on domain and sub-domain (with Studio license)

Elements
1

I have established the online CMS on my main domain and on a sub-domain. On the main domain it works just fine. On the sub-domain I have troubles creating new files and uploading images. Opening a new file does not show the relevant front matter, and for uploading images it is not possible to select a resource folder. Also the preview function does not work on the sub-domain. To illustrate the issue I have uploaded a few screenshots. I would be grateful for a hint how to overcome these issues.

323AAA61-6975-45DD-B8E8-1BCBBD243C29_1_102_a
323AAA61-6975-45DD-B8E8-1BCBBD243C29_1_102_a1566×2008 102 KB

9DCBA1F7-7D93-4B43-9380-5201064E6E18_1_102_a
9DCBA1F7-7D93-4B43-9380-5201064E6E18_1_102_a1651×1906 414 KB

F93384A1-C1EB-400E-B18B-1479B2D6D1E5_1_102_a
F93384A1-C1EB-400E-B18B-1479B2D6D1E5_1_102_a1636×1920 90 KB

90A6C459-E5E3-4558-BC08-1A24C66B0893_1_102_a
90A6C459-E5E3-4558-BC08-1A24C66B0893_1_102_a1650×1904 72.2 KB

FF81BB4B-9A79-4E8B-9A73-A6A39D4425FE_1_102_a
FF81BB4B-9A79-4E8B-9A73-A6A39D4425FE_1_102_a1656×1896 415 KB

2

You have define the frontmatter for each of the folders.

image
image5092×1662 328 KB

If you haven’t defined an image field for the folder, you aren’t shown the field in a new file. Is this what you mean by “for uploading images it is not possible to select a resource folder”?