By default, EPS runs with a very specific set of addresses (you have to configure each address you want to know about, or provide a master public key). If you then add new addresses into Electrum... then EPS needs to be updated with these new addresses, so it can then get that address info from your node.

This often means "rescanning" with EPS several times to get updated info...

EPS can be a bit "problematic" like that if you think you're going to be adding new wallets to Electrum from time to time