"The requested self IP (/Common/selfip_1_1) was not found" keeps on showing in LTM logs

You can search /config directory via SSH for the configuration file with the selfip_1_1 reference. Modify the file, deleting the refernce, and then reload / save the config.

1) SSH into F5 BIG-IP instance and grep for selfip_1_1 in /config directory.

2) Modify the file with the reference, removing it.

3) tmsh load sys config

4) tmsh save sys config

5) Continue via GUI to configuration as usual.