Having read through some of the recent Electrum release notes, I think this issue may have been fixed, although I haven't tested it myself, and reading the code/github is beyond my ability 
If you used the latest version at the timestamp of the OP which is: 3.3.6;there were only two updates that occurred after it that have RBF improvements, but I can't see any minimum recommended bump fee update.
In the latest: Just two [solved] crash reports caused by errors. (#5502 and #5483)
In the later one: Changed/Prioritize another way to add the extra fee. (from deducted from the outputs' amount or change->to add more input(s) if needed)
-edit-
Since it's almost 3months, I've opened a new issue: #5636
Let's see if they will link a duplicate.