The Webserver table has a list of all web servers used by the application.
If the previous server is still listed in the table and enabled, that might cause an issue during the migrations. This happens because the application tries to synchronize the cache with that old server, thinking it is still part of a web farm, and it might fail with errors when it fails to reach it.
It is suggested to delete all entries from the Webserver table after a migration since web servers will be automatically added once they are being used by DNN.
For example, as soon as you launch the newly migrated site, the new server will be added to the list (in the Webserver table), and in case you have a web farm environment, as soon as the second server loads, it will also be added to the list as well.
In conclusion, you need to make sure that only the available servers are listed as enabled in the Webserver table. If you have old servers as disabled, this should not cause any issue, nevertheless, it is a good practice to delete them if you no longer need them.