I've tried it on my workspace. Somehow it can't add the attachment. I did many workaround steps include mounting with the Volume and connect it with R2 Storage, but it didnt work still. No error log, but somehow I know its definitely some error/ malfunction.

So I decide to install the Vikunja docker from their official site, on outside VPS and check the log, easier to do with Linux SSH. It showed up clearly some error related with the attachment. The ./files directory on the host should has the proper permissions (read, write, and execute permission)
By simple syntax I can fix it on Linux VPS using SSH.

But I couldnt find the similar way to detect the error, more ever to fix it on the Railway. No error logs detected and unable to SSH