as Dmitry has mentioned, we indeed implemented a fix for a similar problem in the latest version 3.4.6, could you advise, is that version is installed on your server or are you using oldest one? Also, could you let us know what is the Bitbucket server that you use?
We would need to investigate the issue a little deeper to develop a solution, could you please provide us with the add-on logs? If you’re using v.3.4.6, then the logs can be collected in the add-on UI on Repository Settings - SVN Mirror - Support tab but the Create zip button. In the case of an earlier add-on version, the logs should be collected directly from the server filesystem; repository-specifics logs reside at the following path:
global add-on logs and Bitbucket server logs reside here:
We would need both repository-specific and global add-on logs and bitbucket logs for at least two or three last days.