Sophos Anti-Virus causing Severe lag on MacBook Pro

I'm using Sophos Anti-Virus V 9.9.5, Threat Detection engine 3.77.1, Threat data 5.70 on a MacBook Pro 3.1 GHz Intel Core i7, with 16 GB memory, running Mojave.

I'm getting incredible, work-stupefying lag on my machine, which has only increased over time.  Application stops, and I look at the Sophos icon and it has started spinning.  It happens when switching between tabs in Chrome, opening new links, and even when switching to Word.  It can be as little as 30 seconds, or sometimes require a reboot.  I have disabled live protection to no improvement.  It's gotten to the point where I want to go without virus protection altogether, as it's extremely unpredictable, which can be very disruptive when giving lectures and presentations.

I couldn't tell where to post this, because the Sophos KnowledgeBase index doesn't have an entry just for Anti-Virus.  Your help is most needed, thank you kindly.