Attacking with F is sometimes delayed or cancelled

It happened to me too, and literally just now! With a tentacle as well. It feels like when an enemy successfully hits you, it not only stuns you, but also resets pressing F. You have to press it again for the attack to resume - and it doesn't even always happen. Sometimes it didn't fix it until using ctrl+f, and only then does it finally register, even with a clearly hostile mob. But these repeated clicks mess up any kiting, especially with a fast attacking mob, where you can attack it only once before you need to run away. Right after the tentacle, I went to beat the tall birds, and I practically had to tank them both. And I know it's not the delay issue, because it was my server, and this has never happened before today.

I've been experiencing this too, but not as bad as what's being shown (it's more rare for me, but it could be something I'm doing).