I think you are connection to a phishing server.....
Try to connect to another server (Tools - Network - Server) and right click on a server and select "Use this server". One of the servers i always use is "e2.keff.org", see if that one is in your list.
Let us know if this helped.
Hi djhomeschool,
Thanks for taking the time to reply.
I am most definitely not connected to a phishing server as I am connecting to my own node via Electrum Personal Server. I have figured out (I believe) the issue, and am suggesting an improvement to help others who come across this error

TLDR: RBF has a rule that requires your RBF fee bump to be at least the size of your transaction in bytes above the original fee. (So a transaction that's 225 bytes, paying 1,000 sats can only be bumped by 225 sats or more).
This isn't reflected in Electrum, and took me some research to figure out, so I am suggesting the error message be updated to better reflect it (and potentially the algorithm for suggesting the fee bump too).