Hello,
Thank you for reaching out!
This behavior does indeed sound strange, especially after a factory reset.
Could you navigate to System → Administration → Troubleshoot and generate a troubleshoot file after replicating the issue (plugging the laptop in, performing the pings)? This file can be attached to the original post and it will only be visible to Teltonika moderators. It will give me more insight into what the issue could be.
Also, have you done any configuration other than the initial setup wizard after a factory reset?
Have you tried using a different LAN port on the RUT955?
Best regards,
DaumantasG