If its your theme then its your theme.
What are you using?
Does everything work with another?
A quick test can also be to create a new user and check if everything works there… if it does then you know it is your user configuration.
Image uploading and some other posting activities are restricted to new/inactive users.
If you dont know how to use gitlab then you dont know how to use gitlab…
And it may be a bit early for that, no? How do you know its a bug?
Please see this link for how to provide (and format) information: